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<h3><a href="../../index.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Commands</a><ul>
<li><a class="reference internal" href="#parameters">Parameters</a><ul>
<li><a class="reference internal" href="#positional">Positional</a></li>
<li><a class="reference internal" href="#variable">Variable</a></li>
<li><a class="reference internal" href="#keyword-only-arguments">Keyword-Only Arguments</a></li>
</ul>
</li>
<li><a class="reference internal" href="#invocation-context">Invocation Context</a></li>
<li><a class="reference internal" href="#converters">Converters</a><ul>
<li><a class="reference internal" href="#basic-converters">Basic Converters</a><ul>
<li><a class="reference internal" href="#bool">bool</a></li>
</ul>
</li>
<li><a class="reference internal" href="#advanced-converters">Advanced Converters</a></li>
<li><a class="reference internal" href="#inline-advanced-converters">Inline Advanced Converters</a></li>
<li><a class="reference internal" href="#discord-converters">Discord Converters</a></li>
<li><a class="reference internal" href="#special-converters">Special Converters</a><ul>
<li><a class="reference internal" href="#typing-union">typing.Union</a></li>
<li><a class="reference internal" href="#typing-optional">typing.Optional</a></li>
<li><a class="reference internal" href="#typing-literal">typing.Literal</a></li>
<li><a class="reference internal" href="#greedy">Greedy</a></li>
</ul>
</li>
<li><a class="reference internal" href="#flagconverter">FlagConverter</a><ul>
<li><a class="reference internal" href="#typing-list">typing.List</a></li>
<li><a class="reference internal" href="#typing-tuple">typing.Tuple</a></li>
<li><a class="reference internal" href="#typing-dict">typing.Dict</a></li>
</ul>
</li>
</ul>
</li>
<li><a class="reference internal" href="#error-handling">Error Handling</a></li>
<li><a class="reference internal" href="#checks">Checks</a><ul>
<li><a class="reference internal" href="#global-checks">Global Checks</a></li>
</ul>
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<section id="commands">
<span id="ext-commands-commands"></span><h1>Commands<a class="headerlink" href="#commands" title="Permalink to this headline"></a></h1>
<p>One of the most appealing aspects of the command extension is how easy it is to define commands and
how you can arbitrarily nest groups and commands to have a rich sub-command system.</p>
<p>Commands are defined by attaching it to a regular Python function. The command is then invoked by the user using a similar
signature to the Python function.</p>
<p>For example, in the given command definition:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">foo</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">arg</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span>
</pre></div>
</div>
<p>With the following prefix (<code class="docutils literal notranslate"><span class="pre">$</span></code>), it would be invoked by the user via:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$foo abc
</pre></div>
</div>
<p>A command must always have at least one parameter, <code class="docutils literal notranslate"><span class="pre">ctx</span></code>, which is the <a class="reference internal" href="api.html#discord.ext.commands.Context" title="discord.ext.commands.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a> as the first one.</p>
<p>There are two ways of registering a command. The first one is by using <a class="reference internal" href="api.html#discord.ext.commands.Bot.command" title="discord.ext.commands.Bot.command"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Bot.command()</span></code></a> decorator,
as seen in the example above. The second is using the <a class="reference internal" href="api.html#discord.ext.commands.command" title="discord.ext.commands.command"><code class="xref py py-func docutils literal notranslate"><span class="pre">command()</span></code></a> decorator followed by
<a class="reference internal" href="api.html#discord.ext.commands.Bot.add_command" title="discord.ext.commands.Bot.add_command"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Bot.add_command()</span></code></a> on the instance.</p>
<p>Essentially, these two are equivalent:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">discord.ext</span> <span class="kn">import</span> <span class="n">commands</span>
<span class="n">bot</span> <span class="o">=</span> <span class="n">commands</span><span class="o">.</span><span class="n">Bot</span><span class="p">(</span><span class="n">command_prefix</span><span class="o">=</span><span class="s1">&#39;$&#39;</span><span class="p">)</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="k">pass</span>
<span class="c1"># or:</span>
<span class="nd">@commands</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="k">pass</span>
<span class="n">bot</span><span class="o">.</span><span class="n">add_command</span><span class="p">(</span><span class="n">test</span><span class="p">)</span>
</pre></div>
</div>
<p>Since the <a class="reference internal" href="api.html#discord.ext.commands.Bot.command" title="discord.ext.commands.Bot.command"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Bot.command()</span></code></a> decorator is shorter and easier to comprehend, it will be the one used throughout the
documentation here.</p>
<p>Any parameter that is accepted by the <a class="reference internal" href="api.html#discord.ext.commands.Command" title="discord.ext.commands.Command"><code class="xref py py-class docutils literal notranslate"><span class="pre">Command</span></code></a> constructor can be passed into the decorator. For example, to change
the name to something other than the function would be as simple as doing this:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">&#39;list&#39;</span><span class="p">)</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">_list</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">arg</span><span class="p">):</span>
<span class="k">pass</span>
</pre></div>
</div>
<section id="parameters">
<h2>Parameters<a class="headerlink" href="#parameters" title="Permalink to this headline"></a></h2>
<p>Since we define commands by making Python functions, we also define the argument passing behaviour by the function
parameters.</p>
<p>Certain parameter types do different things in the user side and most forms of parameter types are supported.</p>
<section id="positional">
<h3>Positional<a class="headerlink" href="#positional" title="Permalink to this headline"></a></h3>
<p>The most basic form of parameter passing is the positional parameter. This is where we pass a parameter as-is:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">arg</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span>
</pre></div>
</div>
<p>On the bot using side, you can provide positional arguments by just passing a regular string:</p>
<img alt="../../_images/positional1.png" src="../../_images/positional1.png" />
<p>To make use of a word with spaces in between, you should quote it:</p>
<img alt="../../_images/positional2.png" src="../../_images/positional2.png" />
<p>As a note of warning, if you omit the quotes, you will only get the first word:</p>
<img alt="../../_images/positional3.png" src="../../_images/positional3.png" />
<p>Since positional arguments are just regular Python arguments, you can have as many as you want:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">arg1</span><span class="p">,</span> <span class="n">arg2</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;You passed </span><span class="si">{</span><span class="n">arg1</span><span class="si">}</span><span class="s1"> and </span><span class="si">{</span><span class="n">arg2</span><span class="si">}</span><span class="s1">&#39;</span><span class="p">)</span>
</pre></div>
</div>
</section>
<section id="variable">
<h3>Variable<a class="headerlink" href="#variable" title="Permalink to this headline"></a></h3>
<p>Sometimes you want users to pass in an undetermined number of parameters. The library supports this
similar to how variable list parameters are done in Python:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">):</span>
<span class="n">arguments</span> <span class="o">=</span> <span class="s1">&#39;, &#39;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">args</span><span class="p">)</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="nb">len</span><span class="p">(</span><span class="n">args</span><span class="p">)</span><span class="si">}</span><span class="s1"> arguments: </span><span class="si">{</span><span class="n">arguments</span><span class="si">}</span><span class="s1">&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>This allows our user to accept either one or many arguments as they please. This works similar to positional arguments,
so multi-word parameters should be quoted.</p>
<p>For example, on the bot side:</p>
<img alt="../../_images/variable1.png" src="../../_images/variable1.png" />
<p>If the user wants to input a multi-word argument, they have to quote it like earlier:</p>
<img alt="../../_images/variable2.png" src="../../_images/variable2.png" />
<p>Do note that similar to the Python function behaviour, a user can technically pass no arguments
at all:</p>
<img alt="../../_images/variable3.png" src="../../_images/variable3.png" />
<p>Since the <code class="docutils literal notranslate"><span class="pre">args</span></code> variable is a <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#tuple" title="(in Python v3.9)"><code class="docutils literal notranslate"><span class="pre">tuple</span></code></a>,
you can do anything you would usually do with one.</p>
<div class="admonition-slash-command-only admonition">
<p class="admonition-title">Slash Command Only</p>
<p>This functionally is currently not supported by the slash command API, so is turned into
a single <code class="docutils literal notranslate"><span class="pre">STRING</span></code> parameter on discords end which we do our own parsing on.</p>
</div>
</section>
<section id="keyword-only-arguments">
<h3>Keyword-Only Arguments<a class="headerlink" href="#keyword-only-arguments" title="Permalink to this headline"></a></h3>
<p>When you want to handle parsing of the argument yourself or do not feel like you want to wrap multi-word user input into
quotes, you can ask the library to give you the rest as a single argument. We do this by using a <strong>keyword-only argument</strong>,
seen below:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">arg</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span>
</pre></div>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>You can only have one keyword-only argument due to parsing ambiguities.</p>
</div>
<p>On the bot side, we do not need to quote input with spaces:</p>
<img alt="../../_images/keyword1.png" src="../../_images/keyword1.png" />
<p>Do keep in mind that wrapping it in quotes leaves it as-is:</p>
<img alt="../../_images/keyword2.png" src="../../_images/keyword2.png" />
<p>By default, the keyword-only arguments are stripped of white space to make it easier to work with. This behaviour can be
toggled by the <a class="reference internal" href="api.html#discord.ext.commands.Command.rest_is_raw" title="discord.ext.commands.Command.rest_is_raw"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Command.rest_is_raw</span></code></a> argument in the decorator.</p>
</section>
</section>
<section id="invocation-context">
<span id="ext-commands-context"></span><h2>Invocation Context<a class="headerlink" href="#invocation-context" title="Permalink to this headline"></a></h2>
<p>As seen earlier, every command must take at least a single parameter, called the <a class="reference internal" href="api.html#discord.ext.commands.Context" title="discord.ext.commands.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a>.</p>
<p>This parameter gives you access to something called the “invocation context”. Essentially all the information you need to
know how the command was executed. It contains a lot of useful information:</p>
<ul class="simple">
<li><p><a class="reference internal" href="api.html#discord.ext.commands.Context.guild" title="discord.ext.commands.Context.guild"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Context.guild</span></code></a> to fetch the <a class="reference internal" href="../../api.html#discord.Guild" title="discord.Guild"><code class="xref py py-class docutils literal notranslate"><span class="pre">Guild</span></code></a> of the command, if any.</p></li>
<li><p><a class="reference internal" href="api.html#discord.ext.commands.Context.message" title="discord.ext.commands.Context.message"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Context.message</span></code></a> to fetch the <a class="reference internal" href="../../api.html#discord.Message" title="discord.Message"><code class="xref py py-class docutils literal notranslate"><span class="pre">Message</span></code></a> of the command.</p></li>
<li><p><a class="reference internal" href="api.html#discord.ext.commands.Context.author" title="discord.ext.commands.Context.author"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Context.author</span></code></a> to fetch the <a class="reference internal" href="../../api.html#discord.Member" title="discord.Member"><code class="xref py py-class docutils literal notranslate"><span class="pre">Member</span></code></a> or <a class="reference internal" href="../../api.html#discord.User" title="discord.User"><code class="xref py py-class docutils literal notranslate"><span class="pre">User</span></code></a> that called the command.</p></li>
<li><p><a class="reference internal" href="api.html#discord.ext.commands.Context.send" title="discord.ext.commands.Context.send"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Context.send()</span></code></a> to send a message to the channel the command was used in.</p></li>
</ul>
<p>The context implements the <a class="reference internal" href="../../api.html#discord.abc.Messageable" title="discord.abc.Messageable"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.Messageable</span></code></a> interface, so anything you can do on a <a class="reference internal" href="../../api.html#discord.abc.Messageable" title="discord.abc.Messageable"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.Messageable</span></code></a> you
can do on the <a class="reference internal" href="api.html#discord.ext.commands.Context" title="discord.ext.commands.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a>.</p>
<div class="admonition-slash-command-only admonition">
<p class="admonition-title">Slash Command Only</p>
<p><a class="reference internal" href="api.html#discord.ext.commands.Context.message" title="discord.ext.commands.Context.message"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Context.message</span></code></a> will be fake if in a slash command, it is not
recommended to access if <code class="xref py py-attr docutils literal notranslate"><span class="pre">Context.interaction</span></code> is not None as most
methods will error due to the message not actually existing.</p>
</div>
</section>
<section id="converters">
<h2>Converters<a class="headerlink" href="#converters" title="Permalink to this headline"></a></h2>
<p>Adding bot arguments with function parameters is only the first step in defining your bots command interface. To actually
make use of the arguments, we usually want to convert the data into a target type. We call these
<a class="reference internal" href="api.html#ext-commands-api-converters"><span class="std std-ref">Converters</span></a>.</p>
<p>Converters come in a few flavours:</p>
<ul>
<li><p>A regular callable object that takes an argument as a sole parameter and returns a different type.</p>
<blockquote>
<div><ul class="simple">
<li><p>These range from your own function, to something like <a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">bool</span></code></a> or <a class="reference external" href="https://docs.python.org/3/library/functions.html#int" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>.</p></li>
</ul>
</div></blockquote>
</li>
<li><p>A custom class that inherits from <a class="reference internal" href="api.html#discord.ext.commands.Converter" title="discord.ext.commands.Converter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Converter</span></code></a>.</p></li>
</ul>
<section id="basic-converters">
<span id="ext-commands-basic-converters"></span><h3>Basic Converters<a class="headerlink" href="#basic-converters" title="Permalink to this headline"></a></h3>
<p>At its core, a basic converter is a callable that takes in an argument and turns it into something else.</p>
<p>For example, if we wanted to add two numbers together, we could request that they are turned into integers
for us by specifying the converter:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">add</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">a</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">b</span><span class="p">:</span> <span class="nb">int</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">a</span> <span class="o">+</span> <span class="n">b</span><span class="p">)</span>
</pre></div>
</div>
<p>We specify converters by using something called a <strong>function annotation</strong>. This is a Python 3 exclusive feature that was
introduced in <span class="target" id="index-0"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-3107"><strong>PEP 3107</strong></a>.</p>
<p>This works with any callable, such as a function that would convert a string to all upper-case:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">to_upper</span><span class="p">(</span><span class="n">argument</span><span class="p">):</span>
<span class="k">return</span> <span class="n">argument</span><span class="o">.</span><span class="n">upper</span><span class="p">()</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">up</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">content</span><span class="p">:</span> <span class="n">to_upper</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">content</span><span class="p">)</span>
</pre></div>
</div>
<section id="bool">
<h4>bool<a class="headerlink" href="#bool" title="Permalink to this headline"></a></h4>
<p>Unlike the other basic converters, the <a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">bool</span></code></a> converter is treated slightly different. Instead of casting directly to the <a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">bool</span></code></a> type, which would result in any non-empty argument returning <code class="docutils literal notranslate"><span class="pre">True</span></code>, it instead evaluates the argument as <code class="docutils literal notranslate"><span class="pre">True</span></code> or <code class="docutils literal notranslate"><span class="pre">False</span></code> based on its given content:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">if</span> <span class="n">lowered</span> <span class="ow">in</span> <span class="p">(</span><span class="s1">&#39;yes&#39;</span><span class="p">,</span> <span class="s1">&#39;y&#39;</span><span class="p">,</span> <span class="s1">&#39;true&#39;</span><span class="p">,</span> <span class="s1">&#39;t&#39;</span><span class="p">,</span> <span class="s1">&#39;1&#39;</span><span class="p">,</span> <span class="s1">&#39;enable&#39;</span><span class="p">,</span> <span class="s1">&#39;on&#39;</span><span class="p">):</span>
<span class="k">return</span> <span class="kc">True</span>
<span class="k">elif</span> <span class="n">lowered</span> <span class="ow">in</span> <span class="p">(</span><span class="s1">&#39;no&#39;</span><span class="p">,</span> <span class="s1">&#39;n&#39;</span><span class="p">,</span> <span class="s1">&#39;false&#39;</span><span class="p">,</span> <span class="s1">&#39;f&#39;</span><span class="p">,</span> <span class="s1">&#39;0&#39;</span><span class="p">,</span> <span class="s1">&#39;disable&#39;</span><span class="p">,</span> <span class="s1">&#39;off&#39;</span><span class="p">):</span>
<span class="k">return</span> <span class="kc">False</span>
</pre></div>
</div>
</section>
</section>
<section id="advanced-converters">
<span id="ext-commands-adv-converters"></span><h3>Advanced Converters<a class="headerlink" href="#advanced-converters" title="Permalink to this headline"></a></h3>
<p>Sometimes a basic converter doesnt have enough information that we need. For example, sometimes we want to get some
information from the <a class="reference internal" href="../../api.html#discord.Message" title="discord.Message"><code class="xref py py-class docutils literal notranslate"><span class="pre">Message</span></code></a> that called the command or we want to do some asynchronous processing.</p>
<p>For this, the library provides the <a class="reference internal" href="api.html#discord.ext.commands.Converter" title="discord.ext.commands.Converter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Converter</span></code></a> interface. This allows you to have access to the
<a class="reference internal" href="api.html#discord.ext.commands.Context" title="discord.ext.commands.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a> and have the callable be asynchronous. Defining a custom converter using this interface requires
overriding a single method, <a class="reference internal" href="api.html#discord.ext.commands.Converter.convert" title="discord.ext.commands.Converter.convert"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Converter.convert()</span></code></a>.</p>
<p>An example converter:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">random</span>
<span class="k">class</span> <span class="nc">Slapper</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">Converter</span><span class="p">):</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">convert</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">argument</span><span class="p">):</span>
<span class="n">to_slap</span> <span class="o">=</span> <span class="n">random</span><span class="o">.</span><span class="n">choice</span><span class="p">(</span><span class="n">ctx</span><span class="o">.</span><span class="n">guild</span><span class="o">.</span><span class="n">members</span><span class="p">)</span>
<span class="k">return</span> <span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">ctx</span><span class="o">.</span><span class="n">author</span><span class="si">}</span><span class="s1"> slapped </span><span class="si">{</span><span class="n">to_slap</span><span class="si">}</span><span class="s1"> because *</span><span class="si">{</span><span class="n">argument</span><span class="si">}</span><span class="s1">*&#39;</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">slap</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">reason</span><span class="p">:</span> <span class="n">Slapper</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">reason</span><span class="p">)</span>
</pre></div>
</div>
<p>The converter provided can either be constructed or not. Essentially these two are equivalent:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">slap</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">reason</span><span class="p">:</span> <span class="n">Slapper</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">reason</span><span class="p">)</span>
<span class="c1"># is the same as...</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">slap</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">reason</span><span class="p">:</span> <span class="n">Slapper</span><span class="p">()):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">reason</span><span class="p">)</span>
</pre></div>
</div>
<p>Having the possibility of the converter be constructed allows you to set up some state in the converters <code class="docutils literal notranslate"><span class="pre">__init__</span></code> for
fine tuning the converter. An example of this is actually in the library, <a class="reference internal" href="api.html#discord.ext.commands.clean_content" title="discord.ext.commands.clean_content"><code class="xref py py-class docutils literal notranslate"><span class="pre">clean_content</span></code></a>.</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">clean</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">content</span><span class="p">:</span> <span class="n">commands</span><span class="o">.</span><span class="n">clean_content</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">content</span><span class="p">)</span>
<span class="c1"># or for fine-tuning</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">clean</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">content</span><span class="p">:</span> <span class="n">commands</span><span class="o">.</span><span class="n">clean_content</span><span class="p">(</span><span class="n">use_nicknames</span><span class="o">=</span><span class="kc">False</span><span class="p">)):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">content</span><span class="p">)</span>
</pre></div>
</div>
<p>If a converter fails to convert an argument to its designated target type, the <a class="reference internal" href="api.html#discord.ext.commands.BadArgument" title="discord.ext.commands.BadArgument"><code class="xref py py-exc docutils literal notranslate"><span class="pre">BadArgument</span></code></a> exception must be
raised.</p>
</section>
<section id="inline-advanced-converters">
<h3>Inline Advanced Converters<a class="headerlink" href="#inline-advanced-converters" title="Permalink to this headline"></a></h3>
<p>If we dont want to inherit from <a class="reference internal" href="api.html#discord.ext.commands.Converter" title="discord.ext.commands.Converter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Converter</span></code></a>, we can still provide a converter that has the
advanced functionalities of an advanced converter and save us from specifying two types.</p>
<p>For example, a common idiom would be to have a class and a converter for that class:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span> <span class="nc">JoinDistance</span><span class="p">:</span>
<span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">joined</span><span class="p">,</span> <span class="n">created</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">joined</span> <span class="o">=</span> <span class="n">joined</span>
<span class="bp">self</span><span class="o">.</span><span class="n">created</span> <span class="o">=</span> <span class="n">created</span>
<span class="nd">@property</span>
<span class="k">def</span> <span class="nf">delta</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">joined</span> <span class="o">-</span> <span class="bp">self</span><span class="o">.</span><span class="n">created</span>
<span class="k">class</span> <span class="nc">JoinDistanceConverter</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">MemberConverter</span><span class="p">):</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">convert</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">argument</span><span class="p">):</span>
<span class="n">member</span> <span class="o">=</span> <span class="k">await</span> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="n">convert</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">argument</span><span class="p">)</span>
<span class="k">return</span> <span class="n">JoinDistance</span><span class="p">(</span><span class="n">member</span><span class="o">.</span><span class="n">joined_at</span><span class="p">,</span> <span class="n">member</span><span class="o">.</span><span class="n">created_at</span><span class="p">)</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">delta</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">member</span><span class="p">:</span> <span class="n">JoinDistanceConverter</span><span class="p">):</span>
<span class="n">is_new</span> <span class="o">=</span> <span class="n">member</span><span class="o">.</span><span class="n">delta</span><span class="o">.</span><span class="n">days</span> <span class="o">&lt;</span> <span class="mi">100</span>
<span class="k">if</span> <span class="n">is_new</span><span class="p">:</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s2">&quot;Hey you&#39;re pretty new!&quot;</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s2">&quot;Hm you&#39;re not so new.&quot;</span><span class="p">)</span>
</pre></div>
</div>
<p>This can get tedious, so an inline advanced converter is possible through a <a class="reference external" href="https://docs.python.org/3/library/functions.html#classmethod" title="(in Python v3.9)"><code class="xref py py-func docutils literal notranslate"><span class="pre">classmethod()</span></code></a> inside the type:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span> <span class="nc">JoinDistance</span><span class="p">:</span>
<span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">joined</span><span class="p">,</span> <span class="n">created</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">joined</span> <span class="o">=</span> <span class="n">joined</span>
<span class="bp">self</span><span class="o">.</span><span class="n">created</span> <span class="o">=</span> <span class="n">created</span>
<span class="nd">@classmethod</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">convert</span><span class="p">(</span><span class="bp">cls</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">argument</span><span class="p">):</span>
<span class="n">member</span> <span class="o">=</span> <span class="k">await</span> <span class="n">commands</span><span class="o">.</span><span class="n">MemberConverter</span><span class="p">()</span><span class="o">.</span><span class="n">convert</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">argument</span><span class="p">)</span>
<span class="k">return</span> <span class="bp">cls</span><span class="p">(</span><span class="n">member</span><span class="o">.</span><span class="n">joined_at</span><span class="p">,</span> <span class="n">member</span><span class="o">.</span><span class="n">created_at</span><span class="p">)</span>
<span class="nd">@property</span>
<span class="k">def</span> <span class="nf">delta</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">joined</span> <span class="o">-</span> <span class="bp">self</span><span class="o">.</span><span class="n">created</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">delta</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">member</span><span class="p">:</span> <span class="n">JoinDistance</span><span class="p">):</span>
<span class="n">is_new</span> <span class="o">=</span> <span class="n">member</span><span class="o">.</span><span class="n">delta</span><span class="o">.</span><span class="n">days</span> <span class="o">&lt;</span> <span class="mi">100</span>
<span class="k">if</span> <span class="n">is_new</span><span class="p">:</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s2">&quot;Hey you&#39;re pretty new!&quot;</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s2">&quot;Hm you&#39;re not so new.&quot;</span><span class="p">)</span>
</pre></div>
</div>
</section>
<section id="discord-converters">
<h3>Discord Converters<a class="headerlink" href="#discord-converters" title="Permalink to this headline"></a></h3>
<p>Working with <a class="reference internal" href="../../api.html#discord-api-models"><span class="std std-ref">Discord Models</span></a> is a fairly common thing when defining commands, as a result the library makes
working with them easy.</p>
<p>For example, to receive a <a class="reference internal" href="../../api.html#discord.Member" title="discord.Member"><code class="xref py py-class docutils literal notranslate"><span class="pre">Member</span></code></a> you can just pass it as a converter:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">joined</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">member</span><span class="p">:</span> <span class="n">discord</span><span class="o">.</span><span class="n">Member</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">member</span><span class="si">}</span><span class="s1"> joined on </span><span class="si">{</span><span class="n">member</span><span class="o">.</span><span class="n">joined_at</span><span class="si">}</span><span class="s1">&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>When this command is executed, it attempts to convert the string given into a <a class="reference internal" href="../../api.html#discord.Member" title="discord.Member"><code class="xref py py-class docutils literal notranslate"><span class="pre">Member</span></code></a> and then passes it as a
parameter for the function. This works by checking if the string is a mention, an ID, a nickname, a username + discriminator,
or just a regular username. The default set of converters have been written to be as easy to use as possible.</p>
<p>A lot of discord models work out of the gate as a parameter:</p>
<ul class="simple">
<li><p><a class="reference internal" href="../../api.html#discord.Object" title="discord.Object"><code class="xref py py-class docutils literal notranslate"><span class="pre">Object</span></code></a> (since v2.0)</p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Member" title="discord.Member"><code class="xref py py-class docutils literal notranslate"><span class="pre">Member</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.User" title="discord.User"><code class="xref py py-class docutils literal notranslate"><span class="pre">User</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Message" title="discord.Message"><code class="xref py py-class docutils literal notranslate"><span class="pre">Message</span></code></a> (since v1.1)</p></li>
<li><p><a class="reference internal" href="../../api.html#discord.PartialMessage" title="discord.PartialMessage"><code class="xref py py-class docutils literal notranslate"><span class="pre">PartialMessage</span></code></a> (since v1.7)</p></li>
<li><p><a class="reference internal" href="../../api.html#discord.abc.GuildChannel" title="discord.abc.GuildChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">abc.GuildChannel</span></code></a> (since 2.0)</p></li>
<li><p><a class="reference internal" href="../../api.html#discord.TextChannel" title="discord.TextChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextChannel</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.VoiceChannel" title="discord.VoiceChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">VoiceChannel</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.StageChannel" title="discord.StageChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">StageChannel</span></code></a> (since v1.7)</p></li>
<li><p><a class="reference internal" href="../../api.html#discord.StoreChannel" title="discord.StoreChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">StoreChannel</span></code></a> (since v1.7)</p></li>
<li><p><a class="reference internal" href="../../api.html#discord.CategoryChannel" title="discord.CategoryChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">CategoryChannel</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Invite" title="discord.Invite"><code class="xref py py-class docutils literal notranslate"><span class="pre">Invite</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Guild" title="discord.Guild"><code class="xref py py-class docutils literal notranslate"><span class="pre">Guild</span></code></a> (since v1.7)</p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Role" title="discord.Role"><code class="xref py py-class docutils literal notranslate"><span class="pre">Role</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Game" title="discord.Game"><code class="xref py py-class docutils literal notranslate"><span class="pre">Game</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Colour" title="discord.Colour"><code class="xref py py-class docutils literal notranslate"><span class="pre">Colour</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Emoji" title="discord.Emoji"><code class="xref py py-class docutils literal notranslate"><span class="pre">Emoji</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.PartialEmoji" title="discord.PartialEmoji"><code class="xref py py-class docutils literal notranslate"><span class="pre">PartialEmoji</span></code></a></p></li>
<li><p><a class="reference internal" href="../../api.html#discord.Thread" title="discord.Thread"><code class="xref py py-class docutils literal notranslate"><span class="pre">Thread</span></code></a> (since v2.0)</p></li>
</ul>
<p>Having any of these set as the converter will intelligently convert the argument to the appropriate target type you
specify.</p>
<p>Under the hood, these are implemented by the <a class="reference internal" href="#ext-commands-adv-converters"><span class="std std-ref">Advanced Converters</span></a> interface. A table of the equivalent
converter is given below:</p>
<div class="table-wrapper"><table class="docutils align-default">
<colgroup>
<col style="width: 25%" />
<col style="width: 47%" />
<col style="width: 28%" />
</colgroup>
<tbody>
<tr class="row-odd"><td><p>Discord Class</p></td>
<td><p>Converter</p></td>
<td><p>Supported By Slash Commands</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.Object" title="discord.Object"><code class="xref py py-class docutils literal notranslate"><span class="pre">Object</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.ObjectConverter" title="discord.ext.commands.ObjectConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">ObjectConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.Member" title="discord.Member"><code class="xref py py-class docutils literal notranslate"><span class="pre">Member</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.MemberConverter" title="discord.ext.commands.MemberConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">MemberConverter</span></code></a></p></td>
<td><p>Yes, as type 6 (USER)</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.User" title="discord.User"><code class="xref py py-class docutils literal notranslate"><span class="pre">User</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.UserConverter" title="discord.ext.commands.UserConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">UserConverter</span></code></a></p></td>
<td><p>Yes, as type 6 (USER)</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.Message" title="discord.Message"><code class="xref py py-class docutils literal notranslate"><span class="pre">Message</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.MessageConverter" title="discord.ext.commands.MessageConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">MessageConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.PartialMessage" title="discord.PartialMessage"><code class="xref py py-class docutils literal notranslate"><span class="pre">PartialMessage</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.PartialMessageConverter" title="discord.ext.commands.PartialMessageConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">PartialMessageConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.abc.GuildChannel" title="discord.abc.GuildChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">GuildChannel</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.GuildChannelConverter" title="discord.ext.commands.GuildChannelConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">GuildChannelConverter</span></code></a></p></td>
<td><p>Yes, as type 7 (CHANNEL)</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.TextChannel" title="discord.TextChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextChannel</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.TextChannelConverter" title="discord.ext.commands.TextChannelConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextChannelConverter</span></code></a></p></td>
<td><p>Yes, as type 7 (CHANNEL)</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.VoiceChannel" title="discord.VoiceChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">VoiceChannel</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.VoiceChannelConverter" title="discord.ext.commands.VoiceChannelConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">VoiceChannelConverter</span></code></a></p></td>
<td><p>Yes, as type 7 (CHANNEL)</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.StageChannel" title="discord.StageChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">StageChannel</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.StageChannelConverter" title="discord.ext.commands.StageChannelConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">StageChannelConverter</span></code></a></p></td>
<td><p>Yes, as type 7 (CHANNEL)</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.StoreChannel" title="discord.StoreChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">StoreChannel</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.StoreChannelConverter" title="discord.ext.commands.StoreChannelConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">StoreChannelConverter</span></code></a></p></td>
<td><p>Yes, as type 7 (CHANNEL)</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.CategoryChannel" title="discord.CategoryChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">CategoryChannel</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.CategoryChannelConverter" title="discord.ext.commands.CategoryChannelConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">CategoryChannelConverter</span></code></a></p></td>
<td><p>Yes, as type 7 (CHANNEL)</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.Thread" title="discord.Thread"><code class="xref py py-class docutils literal notranslate"><span class="pre">Thread</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.ThreadConverter" title="discord.ext.commands.ThreadConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">ThreadConverter</span></code></a></p></td>
<td><p>Yes, as type 7 (CHANNEL)</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.Invite" title="discord.Invite"><code class="xref py py-class docutils literal notranslate"><span class="pre">Invite</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.InviteConverter" title="discord.ext.commands.InviteConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">InviteConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.Guild" title="discord.Guild"><code class="xref py py-class docutils literal notranslate"><span class="pre">Guild</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.GuildConverter" title="discord.ext.commands.GuildConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">GuildConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.Role" title="discord.Role"><code class="xref py py-class docutils literal notranslate"><span class="pre">Role</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.RoleConverter" title="discord.ext.commands.RoleConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">RoleConverter</span></code></a></p></td>
<td><p>Yes, as type 8 (ROLE)</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.Game" title="discord.Game"><code class="xref py py-class docutils literal notranslate"><span class="pre">Game</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.GameConverter" title="discord.ext.commands.GameConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">GameConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.Colour" title="discord.Colour"><code class="xref py py-class docutils literal notranslate"><span class="pre">Colour</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.ColourConverter" title="discord.ext.commands.ColourConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">ColourConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="../../api.html#discord.Emoji" title="discord.Emoji"><code class="xref py py-class docutils literal notranslate"><span class="pre">Emoji</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.EmojiConverter" title="discord.ext.commands.EmojiConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">EmojiConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="../../api.html#discord.PartialEmoji" title="discord.PartialEmoji"><code class="xref py py-class docutils literal notranslate"><span class="pre">PartialEmoji</span></code></a></p></td>
<td><p><a class="reference internal" href="api.html#discord.ext.commands.PartialEmojiConverter" title="discord.ext.commands.PartialEmojiConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">PartialEmojiConverter</span></code></a></p></td>
<td><p>Not currently</p></td>
</tr>
</tbody>
</table>
</div><div class="admonition-slash-command-only admonition">
<p class="admonition-title">Slash Command Only</p>
<p>If a slash command is not marked on the table above as supported, it will be sent as type 3 (STRING)
and parsed by normal content parsing, see
<a class="reference external" href="https://discord.com/developers/docs/interactions/application-commands#application-command-object-application-command-option-type">the discord documentation</a>
for all supported types by the API.</p>
</div>
<p>By providing the converter it allows us to use them as building blocks for another converter:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span> <span class="nc">MemberRoles</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">MemberConverter</span><span class="p">):</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">convert</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">argument</span><span class="p">):</span>
<span class="n">member</span> <span class="o">=</span> <span class="k">await</span> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="n">convert</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">argument</span><span class="p">)</span>
<span class="k">return</span> <span class="p">[</span><span class="n">role</span><span class="o">.</span><span class="n">name</span> <span class="k">for</span> <span class="n">role</span> <span class="ow">in</span> <span class="n">member</span><span class="o">.</span><span class="n">roles</span><span class="p">[</span><span class="mi">1</span><span class="p">:]]</span> <span class="c1"># Remove everyone role!</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">roles</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">member</span><span class="p">:</span> <span class="n">MemberRoles</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;Tells you a member&#39;s roles.&quot;&quot;&quot;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s1">&#39;I see the following roles: &#39;</span> <span class="o">+</span> <span class="s1">&#39;, &#39;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">member</span><span class="p">))</span>
</pre></div>
</div>
</section>
<section id="special-converters">
<span id="ext-commands-special-converters"></span><h3>Special Converters<a class="headerlink" href="#special-converters" title="Permalink to this headline"></a></h3>
<p>The command extension also has support for certain converters to allow for more advanced and intricate use cases that go
beyond the generic linear parsing. These converters allow you to introduce some more relaxed and dynamic grammar to your
commands in an easy to use manner.</p>
<section id="typing-union">
<h4>typing.Union<a class="headerlink" href="#typing-union" title="Permalink to this headline"></a></h4>
<p>A <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Union" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Union</span></code></a> is a special type hint that allows for the command to take in any of the specific types instead of
a singular type. For example, given the following:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">typing</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">union</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">what</span><span class="p">:</span> <span class="n">typing</span><span class="o">.</span><span class="n">Union</span><span class="p">[</span><span class="n">discord</span><span class="o">.</span><span class="n">TextChannel</span><span class="p">,</span> <span class="n">discord</span><span class="o">.</span><span class="n">Member</span><span class="p">]):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">what</span><span class="p">)</span>
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">what</span></code> parameter would either take a <a class="reference internal" href="../../api.html#discord.TextChannel" title="discord.TextChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">discord.TextChannel</span></code></a> converter or a <a class="reference internal" href="../../api.html#discord.Member" title="discord.Member"><code class="xref py py-class docutils literal notranslate"><span class="pre">discord.Member</span></code></a> converter.
The way this works is through a left-to-right order. It first attempts to convert the input to a
<a class="reference internal" href="../../api.html#discord.TextChannel" title="discord.TextChannel"><code class="xref py py-class docutils literal notranslate"><span class="pre">discord.TextChannel</span></code></a>, and if it fails it tries to convert it to a <a class="reference internal" href="../../api.html#discord.Member" title="discord.Member"><code class="xref py py-class docutils literal notranslate"><span class="pre">discord.Member</span></code></a>. If all converters fail,
then a special error is raised, <a class="reference internal" href="api.html#discord.ext.commands.BadUnionArgument" title="discord.ext.commands.BadUnionArgument"><code class="xref py py-exc docutils literal notranslate"><span class="pre">BadUnionArgument</span></code></a>.</p>
<p>Note that any valid converter discussed above can be passed in to the argument list of a <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Union" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Union</span></code></a>.</p>
<div class="admonition-slash-command-only admonition">
<p class="admonition-title">Slash Command Only</p>
<p>These are not currently supported by the Discord API and will be sent as type 3 (STRING)</p>
</div>
</section>
<section id="typing-optional">
<h4>typing.Optional<a class="headerlink" href="#typing-optional" title="Permalink to this headline"></a></h4>
<p>A <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Optional" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Optional</span></code></a> is a special type hint that allows for “back-referencing” behaviour. If the converter fails to
parse into the specified type, the parser will skip the parameter and then either <code class="docutils literal notranslate"><span class="pre">None</span></code> or the specified default will be
passed into the parameter instead. The parser will then continue on to the next parameters and converters, if any.</p>
<p>Consider the following example:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">typing</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">bottles</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">amount</span><span class="p">:</span> <span class="n">typing</span><span class="o">.</span><span class="n">Optional</span><span class="p">[</span><span class="nb">int</span><span class="p">]</span> <span class="o">=</span> <span class="mi">99</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">liquid</span><span class="o">=</span><span class="s2">&quot;beer&quot;</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">amount</span><span class="si">}</span><span class="s1"> bottles of </span><span class="si">{</span><span class="n">liquid</span><span class="si">}</span><span class="s1"> on the wall!&#39;</span><span class="p">)</span>
</pre></div>
</div>
<img alt="../../_images/optional1.png" src="../../_images/optional1.png" />
<p>In this example, since the argument could not be converted into an <code class="docutils literal notranslate"><span class="pre">int</span></code>, the default of <code class="docutils literal notranslate"><span class="pre">99</span></code> is passed and the parser
resumes handling, which in this case would be to pass it into the <code class="docutils literal notranslate"><span class="pre">liquid</span></code> parameter.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This converter only works in regular positional parameters, not variable parameters or keyword-only parameters.</p>
</div>
</section>
<section id="typing-literal">
<h4>typing.Literal<a class="headerlink" href="#typing-literal" title="Permalink to this headline"></a></h4>
<p>A <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Literal" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Literal</span></code></a> is a special type hint that requires the passed parameter to be equal to one of the listed values
after being converted to the same type. For example, given the following:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">typing</span> <span class="kn">import</span> <span class="n">Literal</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">shop</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">buy_sell</span><span class="p">:</span> <span class="n">Literal</span><span class="p">[</span><span class="s1">&#39;buy&#39;</span><span class="p">,</span> <span class="s1">&#39;sell&#39;</span><span class="p">],</span> <span class="n">amount</span><span class="p">:</span> <span class="n">Literal</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">],</span> <span class="o">*</span><span class="p">,</span> <span class="n">item</span><span class="p">:</span> <span class="nb">str</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">buy_sell</span><span class="o">.</span><span class="n">capitalize</span><span class="p">()</span><span class="si">}</span><span class="s1">ing </span><span class="si">{</span><span class="n">amount</span><span class="si">}</span><span class="s1"> </span><span class="si">{</span><span class="n">item</span><span class="si">}</span><span class="s1">(s)!&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">buy_sell</span></code> parameter must be either the literal string <code class="docutils literal notranslate"><span class="pre">&quot;buy&quot;</span></code> or <code class="docutils literal notranslate"><span class="pre">&quot;sell&quot;</span></code> and <code class="docutils literal notranslate"><span class="pre">amount</span></code> must convert to the
<code class="docutils literal notranslate"><span class="pre">int</span></code> <code class="docutils literal notranslate"><span class="pre">1</span></code> or <code class="docutils literal notranslate"><span class="pre">2</span></code>. If <code class="docutils literal notranslate"><span class="pre">buy_sell</span></code> or <code class="docutils literal notranslate"><span class="pre">amount</span></code> dont match any value, then a special error is raised,
<a class="reference internal" href="api.html#discord.ext.commands.BadLiteralArgument" title="discord.ext.commands.BadLiteralArgument"><code class="xref py py-exc docutils literal notranslate"><span class="pre">BadLiteralArgument</span></code></a>. Any literal values can be mixed and matched within the same <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Literal" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Literal</span></code></a> converter.</p>
<p>Note that <code class="docutils literal notranslate"><span class="pre">typing.Literal[True]</span></code> and <code class="docutils literal notranslate"><span class="pre">typing.Literal[False]</span></code> still follow the <a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">bool</span></code></a> converter rules.</p>
</section>
<section id="greedy">
<h4>Greedy<a class="headerlink" href="#greedy" title="Permalink to this headline"></a></h4>
<p>The <a class="reference internal" href="api.html#discord.ext.commands.Greedy" title="discord.ext.commands.Greedy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Greedy</span></code></a> converter is a generalisation of the <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Optional" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Optional</span></code></a> converter, except applied
to a list of arguments. In simple terms, this means that it tries to convert as much as it can until it cant convert
any further.</p>
<p>Consider the following example:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">slap</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">members</span><span class="p">:</span> <span class="n">commands</span><span class="o">.</span><span class="n">Greedy</span><span class="p">[</span><span class="n">discord</span><span class="o">.</span><span class="n">Member</span><span class="p">],</span> <span class="o">*</span><span class="p">,</span> <span class="n">reason</span><span class="o">=</span><span class="s1">&#39;no reason&#39;</span><span class="p">):</span>
<span class="n">slapped</span> <span class="o">=</span> <span class="s2">&quot;, &quot;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">x</span><span class="o">.</span><span class="n">name</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="n">members</span><span class="p">)</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">slapped</span><span class="si">}</span><span class="s1"> just got slapped for </span><span class="si">{</span><span class="n">reason</span><span class="si">}</span><span class="s1">&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>When invoked, it allows for any number of members to be passed in:</p>
<img alt="../../_images/greedy1.png" src="../../_images/greedy1.png" />
<p>The type passed when using this converter depends on the parameter type that it is being attached to:</p>
<ul class="simple">
<li><p>Positional parameter types will receive either the default parameter or a <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#list" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a> of the converted values.</p></li>
<li><p>Variable parameter types will be a <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#tuple" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">tuple</span></code></a> as usual.</p></li>
<li><p>Keyword-only parameter types will be the same as if <a class="reference internal" href="api.html#discord.ext.commands.Greedy" title="discord.ext.commands.Greedy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Greedy</span></code></a> was not passed at all.</p></li>
</ul>
<p><a class="reference internal" href="api.html#discord.ext.commands.Greedy" title="discord.ext.commands.Greedy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Greedy</span></code></a> parameters can also be made optional by specifying an optional value.</p>
<p>When mixed with the <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Optional" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Optional</span></code></a> converter you can provide simple and expressive command invocation syntaxes:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">typing</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">ban</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">members</span><span class="p">:</span> <span class="n">commands</span><span class="o">.</span><span class="n">Greedy</span><span class="p">[</span><span class="n">discord</span><span class="o">.</span><span class="n">Member</span><span class="p">],</span>
<span class="n">delete_days</span><span class="p">:</span> <span class="n">typing</span><span class="o">.</span><span class="n">Optional</span><span class="p">[</span><span class="nb">int</span><span class="p">]</span> <span class="o">=</span> <span class="mi">0</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span>
<span class="n">reason</span><span class="p">:</span> <span class="nb">str</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;Mass bans members with an optional delete_days parameter&quot;&quot;&quot;</span>
<span class="k">for</span> <span class="n">member</span> <span class="ow">in</span> <span class="n">members</span><span class="p">:</span>
<span class="k">await</span> <span class="n">member</span><span class="o">.</span><span class="n">ban</span><span class="p">(</span><span class="n">delete_message_days</span><span class="o">=</span><span class="n">delete_days</span><span class="p">,</span> <span class="n">reason</span><span class="o">=</span><span class="n">reason</span><span class="p">)</span>
</pre></div>
</div>
<p>This command can be invoked any of the following ways:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>$ban @Member @Member2 spam bot
$ban @Member @Member2 7 spam bot
$ban @Member spam
</pre></div>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>The usage of <a class="reference internal" href="api.html#discord.ext.commands.Greedy" title="discord.ext.commands.Greedy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Greedy</span></code></a> and <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Optional" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Optional</span></code></a> are powerful and useful, however as a
price, they open you up to some parsing ambiguities that might surprise some people.</p>
<p>For example, a signature expecting a <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Optional" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Optional</span></code></a> of a <a class="reference internal" href="../../api.html#discord.Member" title="discord.Member"><code class="xref py py-class docutils literal notranslate"><span class="pre">discord.Member</span></code></a> followed by a
<a class="reference external" href="https://docs.python.org/3/library/functions.html#int" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a> could catch a member named after a number due to the different ways a
<a class="reference internal" href="api.html#discord.ext.commands.MemberConverter" title="discord.ext.commands.MemberConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">MemberConverter</span></code></a> decides to fetch members. You should take care to not introduce
unintended parsing ambiguities in your code. One technique would be to clamp down the expected syntaxes
allowed through custom converters or reordering the parameters to minimise clashes.</p>
<p>To help aid with some parsing ambiguities, <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#str" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <code class="docutils literal notranslate"><span class="pre">None</span></code>, <a class="reference external" href="https://docs.python.org/3/library/typing.html#typing.Optional" title="(in Python v3.9)"><code class="xref py py-data docutils literal notranslate"><span class="pre">typing.Optional</span></code></a> and
<a class="reference internal" href="api.html#discord.ext.commands.Greedy" title="discord.ext.commands.Greedy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Greedy</span></code></a> are forbidden as parameters for the <a class="reference internal" href="api.html#discord.ext.commands.Greedy" title="discord.ext.commands.Greedy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Greedy</span></code></a> converter.</p>
</div>
</section>
</section>
<section id="flagconverter">
<span id="ext-commands-flag-converter"></span><h3>FlagConverter<a class="headerlink" href="#flagconverter" title="Permalink to this headline"></a></h3>
<div class="versionadded">
<p><span class="versionmodified added">New in version 2.0.</span></p>
</div>
<p>A <a class="reference internal" href="api.html#discord.ext.commands.FlagConverter" title="discord.ext.commands.FlagConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">FlagConverter</span></code></a> allows the user to specify user-friendly “flags” using <span class="target" id="index-1"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0526"><strong>PEP 526</strong></a> type annotations
or a syntax more reminiscent of the <a class="reference external" href="https://docs.python.org/3/library/dataclasses.html#module-dataclasses" title="(in Python v3.9)"><code class="docutils literal notranslate"><span class="pre">dataclasses</span></code></a> module.</p>
<p>For example, the following code:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">discord.ext</span> <span class="kn">import</span> <span class="n">commands</span>
<span class="kn">import</span> <span class="nn">discord</span>
<span class="k">class</span> <span class="nc">BanFlags</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">FlagConverter</span><span class="p">):</span>
<span class="n">member</span><span class="p">:</span> <span class="n">discord</span><span class="o">.</span><span class="n">Member</span>
<span class="n">reason</span><span class="p">:</span> <span class="nb">str</span>
<span class="n">days</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">1</span>
<span class="nd">@commands</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">ban</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">flags</span><span class="p">:</span> <span class="n">BanFlags</span><span class="p">):</span>
<span class="n">plural</span> <span class="o">=</span> <span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">flags</span><span class="o">.</span><span class="n">days</span><span class="si">}</span><span class="s1"> days&#39;</span> <span class="k">if</span> <span class="n">flags</span><span class="o">.</span><span class="n">days</span> <span class="o">!=</span> <span class="mi">1</span> <span class="k">else</span> <span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">flags</span><span class="o">.</span><span class="n">days</span><span class="si">}</span><span class="s1"> day&#39;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;Banned </span><span class="si">{</span><span class="n">flags</span><span class="o">.</span><span class="n">member</span><span class="si">}</span><span class="s1"> for </span><span class="si">{</span><span class="n">flags</span><span class="o">.</span><span class="n">reason</span><span class="si">!r}</span><span class="s1"> (deleted </span><span class="si">{</span><span class="n">plural</span><span class="si">}</span><span class="s1"> worth of messages)&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>Allows the user to invoke the command using a simple flag-like syntax:</p>
<img alt="../../_images/flags1.png" src="../../_images/flags1.png" />
<p>Flags use a syntax that allows the user to not require quotes when passing in values to the flag. The goal of the
flag syntax is to be as user-friendly as possible. This makes flags a good choice for complicated commands that can have
multiple knobs to turn or simulating keyword-only parameters in your external command interface. <strong>It is recommended to use
keyword-only parameters with the flag converter</strong>. This ensures proper parsing and behaviour with quoting.</p>
<p>Internally, the <a class="reference internal" href="api.html#discord.ext.commands.FlagConverter" title="discord.ext.commands.FlagConverter"><code class="xref py py-class docutils literal notranslate"><span class="pre">FlagConverter</span></code></a> class examines the class to find flags. A flag can either be a
class variable with a type annotation or a class variable thats been assigned the result of the <a class="reference internal" href="api.html#discord.ext.commands.flag" title="discord.ext.commands.flag"><code class="xref py py-func docutils literal notranslate"><span class="pre">flag()</span></code></a>
function. These flags are then used to define the interface that your users will use. The annotations correspond to
the converters that the flag arguments must adhere to.</p>
<p>For most use cases, no extra work is required to define flags. However, if customisation is needed to control the flag name
or the default value then the <a class="reference internal" href="api.html#discord.ext.commands.flag" title="discord.ext.commands.flag"><code class="xref py py-func docutils literal notranslate"><span class="pre">flag()</span></code></a> function can come in handy:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">typing</span> <span class="kn">import</span> <span class="n">List</span>
<span class="k">class</span> <span class="nc">BanFlags</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">FlagConverter</span><span class="p">):</span>
<span class="n">members</span><span class="p">:</span> <span class="n">List</span><span class="p">[</span><span class="n">discord</span><span class="o">.</span><span class="n">Member</span><span class="p">]</span> <span class="o">=</span> <span class="n">commands</span><span class="o">.</span><span class="n">flag</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">&#39;member&#39;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="k">lambda</span> <span class="n">ctx</span><span class="p">:</span> <span class="p">[])</span>
</pre></div>
</div>
<p>This tells the parser that the <code class="docutils literal notranslate"><span class="pre">members</span></code> attribute is mapped to a flag named <code class="docutils literal notranslate"><span class="pre">member</span></code> and that
the default value is an empty list. For greater customisability, the default can either be a value or a callable
that takes the <a class="reference internal" href="api.html#discord.ext.commands.Context" title="discord.ext.commands.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a> as a sole parameter. This callable can either be a function or a coroutine.</p>
<p>In order to customise the flag syntax we also have a few options that can be passed to the class parameter list:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="c1"># --hello world syntax</span>
<span class="k">class</span> <span class="nc">PosixLikeFlags</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">FlagConverter</span><span class="p">,</span> <span class="n">delimiter</span><span class="o">=</span><span class="s1">&#39; &#39;</span><span class="p">,</span> <span class="n">prefix</span><span class="o">=</span><span class="s1">&#39;--&#39;</span><span class="p">):</span>
<span class="n">hello</span><span class="p">:</span> <span class="nb">str</span>
<span class="c1"># /make food</span>
<span class="k">class</span> <span class="nc">WindowsLikeFlags</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">FlagConverter</span><span class="p">,</span> <span class="n">prefix</span><span class="o">=</span><span class="s1">&#39;/&#39;</span><span class="p">,</span> <span class="n">delimiter</span><span class="o">=</span><span class="s1">&#39;&#39;</span><span class="p">):</span>
<span class="n">make</span><span class="p">:</span> <span class="nb">str</span>
<span class="c1"># TOPIC: not allowed nsfw: yes Slowmode: 100</span>
<span class="k">class</span> <span class="nc">Settings</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">FlagConverter</span><span class="p">,</span> <span class="n">case_insensitive</span><span class="o">=</span><span class="kc">True</span><span class="p">):</span>
<span class="n">topic</span><span class="p">:</span> <span class="n">Optional</span><span class="p">[</span><span class="nb">str</span><span class="p">]</span>
<span class="n">nsfw</span><span class="p">:</span> <span class="n">Optional</span><span class="p">[</span><span class="nb">bool</span><span class="p">]</span>
<span class="n">slowmode</span><span class="p">:</span> <span class="n">Optional</span><span class="p">[</span><span class="nb">int</span><span class="p">]</span>
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Despite the similarities in these examples to command like arguments, the syntax and parser is not
a command line parser. The syntax is mainly inspired by Discords search bar input and as a result
all flags need a corresponding value.</p>
</div>
<div class="admonition-slash-command-only admonition">
<p class="admonition-title">Slash Command Only</p>
<p>As these are built very similar to slash command options, they are converted into options and parsed
back into flags when the slash command is executed.</p>
</div>
<p>The flag converter is similar to regular commands and allows you to use most types of converters
(with the exception of <a class="reference internal" href="api.html#discord.ext.commands.Greedy" title="discord.ext.commands.Greedy"><code class="xref py py-class docutils literal notranslate"><span class="pre">Greedy</span></code></a>) as the type annotation. Some extra support is added for specific
annotations as described below.</p>
<section id="typing-list">
<h4>typing.List<a class="headerlink" href="#typing-list" title="Permalink to this headline"></a></h4>
<p>If a list is given as a flag annotation it tells the parser that the argument can be passed multiple times.</p>
<p>For example, augmenting the example above:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">discord.ext</span> <span class="kn">import</span> <span class="n">commands</span>
<span class="kn">from</span> <span class="nn">typing</span> <span class="kn">import</span> <span class="n">List</span>
<span class="kn">import</span> <span class="nn">discord</span>
<span class="k">class</span> <span class="nc">BanFlags</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">FlagConverter</span><span class="p">):</span>
<span class="n">members</span><span class="p">:</span> <span class="n">List</span><span class="p">[</span><span class="n">discord</span><span class="o">.</span><span class="n">Member</span><span class="p">]</span> <span class="o">=</span> <span class="n">commands</span><span class="o">.</span><span class="n">flag</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">&#39;member&#39;</span><span class="p">)</span>
<span class="n">reason</span><span class="p">:</span> <span class="nb">str</span>
<span class="n">days</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">1</span>
<span class="nd">@commands</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">ban</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">flags</span><span class="p">:</span> <span class="n">BanFlags</span><span class="p">):</span>
<span class="k">for</span> <span class="n">member</span> <span class="ow">in</span> <span class="n">flags</span><span class="o">.</span><span class="n">members</span><span class="p">:</span>
<span class="k">await</span> <span class="n">member</span><span class="o">.</span><span class="n">ban</span><span class="p">(</span><span class="n">reason</span><span class="o">=</span><span class="n">flags</span><span class="o">.</span><span class="n">reason</span><span class="p">,</span> <span class="n">delete_message_days</span><span class="o">=</span><span class="n">flags</span><span class="o">.</span><span class="n">days</span><span class="p">)</span>
<span class="n">members</span> <span class="o">=</span> <span class="s1">&#39;, &#39;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="nb">str</span><span class="p">(</span><span class="n">member</span><span class="p">)</span> <span class="k">for</span> <span class="n">member</span> <span class="ow">in</span> <span class="n">flags</span><span class="o">.</span><span class="n">members</span><span class="p">)</span>
<span class="n">plural</span> <span class="o">=</span> <span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">flags</span><span class="o">.</span><span class="n">days</span><span class="si">}</span><span class="s1"> days&#39;</span> <span class="k">if</span> <span class="n">flags</span><span class="o">.</span><span class="n">days</span> <span class="o">!=</span> <span class="mi">1</span> <span class="k">else</span> <span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">flags</span><span class="o">.</span><span class="n">days</span><span class="si">}</span><span class="s1"> day&#39;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="sa">f</span><span class="s1">&#39;Banned </span><span class="si">{</span><span class="n">members</span><span class="si">}</span><span class="s1"> for </span><span class="si">{</span><span class="n">flags</span><span class="o">.</span><span class="n">reason</span><span class="si">!r}</span><span class="s1"> (deleted </span><span class="si">{</span><span class="n">plural</span><span class="si">}</span><span class="s1"> worth of messages)&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>This is called by repeatedly specifying the flag:</p>
<img alt="../../_images/flags2.png" src="../../_images/flags2.png" />
</section>
<section id="typing-tuple">
<h4>typing.Tuple<a class="headerlink" href="#typing-tuple" title="Permalink to this headline"></a></h4>
<p>Since the above syntax can be a bit repetitive when specifying a flag many times, the <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#tuple" title="(in Python v3.9)"><code class="docutils literal notranslate"><span class="pre">tuple</span></code></a> type annotation
allows for “greedy-like” semantics using a variadic tuple:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">discord.ext</span> <span class="kn">import</span> <span class="n">commands</span>
<span class="kn">from</span> <span class="nn">typing</span> <span class="kn">import</span> <span class="n">Tuple</span>
<span class="kn">import</span> <span class="nn">discord</span>
<span class="k">class</span> <span class="nc">BanFlags</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">FlagConverter</span><span class="p">):</span>
<span class="n">members</span><span class="p">:</span> <span class="n">Tuple</span><span class="p">[</span><span class="n">discord</span><span class="o">.</span><span class="n">Member</span><span class="p">,</span> <span class="o">...</span><span class="p">]</span>
<span class="n">reason</span><span class="p">:</span> <span class="nb">str</span>
<span class="n">days</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">1</span>
</pre></div>
</div>
<p>This allows the previous <code class="docutils literal notranslate"><span class="pre">ban</span></code> command to be called like this:</p>
<img alt="../../_images/flags3.png" src="../../_images/flags3.png" />
<p>The <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#tuple" title="(in Python v3.9)"><code class="docutils literal notranslate"><span class="pre">tuple</span></code></a> annotation also allows for parsing of pairs. For example, given the following code:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="c1"># point: 10 11 point: 12 13</span>
<span class="k">class</span> <span class="nc">Coordinates</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">FlagConverter</span><span class="p">):</span>
<span class="n">point</span><span class="p">:</span> <span class="n">Tuple</span><span class="p">[</span><span class="nb">int</span><span class="p">,</span> <span class="nb">int</span><span class="p">]</span>
</pre></div>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Due to potential parsing ambiguities, the parser expects tuple arguments to be quoted
if they require spaces. So if one of the inner types is <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#str" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> and the argument requires spaces
then quotes should be used to disambiguate it from the other element of the tuple.</p>
</div>
</section>
<section id="typing-dict">
<h4>typing.Dict<a class="headerlink" href="#typing-dict" title="Permalink to this headline"></a></h4>
<p>A <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#dict" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> annotation is functionally equivalent to <code class="docutils literal notranslate"><span class="pre">List[Tuple[K,</span> <span class="pre">V]]</span></code> except with the return type
given as a <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#dict" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> rather than a <a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#list" title="(in Python v3.9)"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a>.</p>
</section>
</section>
</section>
<section id="error-handling">
<span id="ext-commands-error-handler"></span><h2>Error Handling<a class="headerlink" href="#error-handling" title="Permalink to this headline"></a></h2>
<p>When our commands fail to parse we will, by default, receive a noisy error in <code class="docutils literal notranslate"><span class="pre">stderr</span></code> of our console that tells us
that an error has happened and has been silently ignored.</p>
<p>In order to handle our errors, we must use something called an error handler. There is a global error handler, called
<a class="reference internal" href="api.html#discord.discord.ext.commands.on_command_error" title="discord.discord.ext.commands.on_command_error"><code class="xref py py-func docutils literal notranslate"><span class="pre">on_command_error()</span></code></a> which works like any other event in the <a class="reference internal" href="../../api.html#discord-api-events"><span class="std std-ref">Event Reference</span></a>. This global error handler is
called for every error reached.</p>
<p>Most of the time however, we want to handle an error local to the command itself. Luckily, commands come with local error
handlers that allow us to do just that. First we decorate an error handler function with <a class="reference internal" href="api.html#discord.ext.commands.Command.error" title="discord.ext.commands.Command.error"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Command.error()</span></code></a>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">info</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">member</span><span class="p">:</span> <span class="n">discord</span><span class="o">.</span><span class="n">Member</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;Tells you some info about the member.&quot;&quot;&quot;</span>
<span class="n">msg</span> <span class="o">=</span> <span class="sa">f</span><span class="s1">&#39;</span><span class="si">{</span><span class="n">member</span><span class="si">}</span><span class="s1"> joined on </span><span class="si">{</span><span class="n">member</span><span class="o">.</span><span class="n">joined_at</span><span class="si">}</span><span class="s1"> and has </span><span class="si">{</span><span class="nb">len</span><span class="p">(</span><span class="n">member</span><span class="o">.</span><span class="n">roles</span><span class="p">)</span><span class="si">}</span><span class="s1"> roles.&#39;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">msg</span><span class="p">)</span>
<span class="nd">@info</span><span class="o">.</span><span class="n">error</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">info_error</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">error</span><span class="p">):</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">error</span><span class="p">,</span> <span class="n">commands</span><span class="o">.</span><span class="n">BadArgument</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s1">&#39;I could not find that member...&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>The first parameter of the error handler is the <a class="reference internal" href="api.html#discord.ext.commands.Context" title="discord.ext.commands.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a> while the second one is an exception that is derived from
<a class="reference internal" href="api.html#discord.ext.commands.CommandError" title="discord.ext.commands.CommandError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CommandError</span></code></a>. A list of errors is found in the <a class="reference internal" href="api.html#ext-commands-api-errors"><span class="std std-ref">Exceptions</span></a> page of the documentation.</p>
</section>
<section id="checks">
<h2>Checks<a class="headerlink" href="#checks" title="Permalink to this headline"></a></h2>
<p>There are cases when we dont want a user to use our commands. They dont have permissions to do so or maybe we blocked
them from using our bot earlier. The commands extension comes with full support for these things in a concept called a
<a class="reference internal" href="api.html#ext-commands-api-checks"><span class="std std-ref">Checks</span></a>.</p>
<p>A check is a basic predicate that can take in a <a class="reference internal" href="api.html#discord.ext.commands.Context" title="discord.ext.commands.Context"><code class="xref py py-class docutils literal notranslate"><span class="pre">Context</span></code></a> as its sole parameter. Within it, you have the following
options:</p>
<ul>
<li><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> to signal that the person can run the command.</p></li>
<li><p>Return <code class="docutils literal notranslate"><span class="pre">False</span></code> to signal that the person cannot run the command.</p></li>
<li><p>Raise a <a class="reference internal" href="api.html#discord.ext.commands.CommandError" title="discord.ext.commands.CommandError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CommandError</span></code></a> derived exception to signal the person cannot run the command.</p>
<blockquote>
<div><ul class="simple">
<li><p>This allows you to have custom error messages for you to handle in the
<a class="reference internal" href="#ext-commands-error-handler"><span class="std std-ref">error handlers</span></a>.</p></li>
</ul>
</div></blockquote>
</li>
</ul>
<p>To register a check for a command, we would have two ways of doing so. The first is using the <a class="reference internal" href="api.html#discord.ext.commands.check" title="discord.ext.commands.check"><code class="xref py py-meth docutils literal notranslate"><span class="pre">check()</span></code></a>
decorator. For example:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">async</span> <span class="k">def</span> <span class="nf">is_owner</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="k">return</span> <span class="n">ctx</span><span class="o">.</span><span class="n">author</span><span class="o">.</span><span class="n">id</span> <span class="o">==</span> <span class="mi">316026178463072268</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">&#39;eval&#39;</span><span class="p">)</span>
<span class="nd">@commands</span><span class="o">.</span><span class="n">check</span><span class="p">(</span><span class="n">is_owner</span><span class="p">)</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">_eval</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">code</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;A bad example of an eval command&quot;&quot;&quot;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="nb">eval</span><span class="p">(</span><span class="n">code</span><span class="p">))</span>
</pre></div>
</div>
<p>This would only evaluate the command if the function <code class="docutils literal notranslate"><span class="pre">is_owner</span></code> returns <code class="docutils literal notranslate"><span class="pre">True</span></code>. Sometimes we re-use a check often and
want to split it into its own decorator. To do that we can just add another level of depth:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">is_owner</span><span class="p">():</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">predicate</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="k">return</span> <span class="n">ctx</span><span class="o">.</span><span class="n">author</span><span class="o">.</span><span class="n">id</span> <span class="o">==</span> <span class="mi">316026178463072268</span>
<span class="k">return</span> <span class="n">commands</span><span class="o">.</span><span class="n">check</span><span class="p">(</span><span class="n">predicate</span><span class="p">)</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">&#39;eval&#39;</span><span class="p">)</span>
<span class="nd">@is_owner</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">_eval</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">code</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;A bad example of an eval command&quot;&quot;&quot;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="nb">eval</span><span class="p">(</span><span class="n">code</span><span class="p">))</span>
</pre></div>
</div>
<p>Since an owner check is so common, the library provides it for you (<a class="reference internal" href="api.html#discord.ext.commands.is_owner" title="discord.ext.commands.is_owner"><code class="xref py py-func docutils literal notranslate"><span class="pre">is_owner()</span></code></a>):</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">&#39;eval&#39;</span><span class="p">)</span>
<span class="nd">@commands</span><span class="o">.</span><span class="n">is_owner</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">_eval</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="o">*</span><span class="p">,</span> <span class="n">code</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;A bad example of an eval command&quot;&quot;&quot;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="nb">eval</span><span class="p">(</span><span class="n">code</span><span class="p">))</span>
</pre></div>
</div>
<p>When multiple checks are specified, <strong>all</strong> of them must be <code class="docutils literal notranslate"><span class="pre">True</span></code>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">is_in_guild</span><span class="p">(</span><span class="n">guild_id</span><span class="p">):</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">predicate</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="k">return</span> <span class="n">ctx</span><span class="o">.</span><span class="n">guild</span> <span class="ow">and</span> <span class="n">ctx</span><span class="o">.</span><span class="n">guild</span><span class="o">.</span><span class="n">id</span> <span class="o">==</span> <span class="n">guild_id</span>
<span class="k">return</span> <span class="n">commands</span><span class="o">.</span><span class="n">check</span><span class="p">(</span><span class="n">predicate</span><span class="p">)</span>
<span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="nd">@commands</span><span class="o">.</span><span class="n">is_owner</span><span class="p">()</span>
<span class="nd">@is_in_guild</span><span class="p">(</span><span class="mi">41771983423143937</span><span class="p">)</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">secretguilddata</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;super secret stuff&quot;&quot;&quot;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s1">&#39;secret stuff&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>If any of those checks fail in the example above, then the command will not be run.</p>
<p>When an error happens, the error is propagated to the <a class="reference internal" href="#ext-commands-error-handler"><span class="std std-ref">error handlers</span></a>. If you do not
raise a custom <a class="reference internal" href="api.html#discord.ext.commands.CommandError" title="discord.ext.commands.CommandError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CommandError</span></code></a> derived exception, then it will get wrapped up into a
<a class="reference internal" href="api.html#discord.ext.commands.CheckFailure" title="discord.ext.commands.CheckFailure"><code class="xref py py-exc docutils literal notranslate"><span class="pre">CheckFailure</span></code></a> exception as so:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">command</span><span class="p">()</span>
<span class="nd">@commands</span><span class="o">.</span><span class="n">is_owner</span><span class="p">()</span>
<span class="nd">@is_in_guild</span><span class="p">(</span><span class="mi">41771983423143937</span><span class="p">)</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">secretguilddata</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;super secret stuff&quot;&quot;&quot;</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s1">&#39;secret stuff&#39;</span><span class="p">)</span>
<span class="nd">@secretguilddata</span><span class="o">.</span><span class="n">error</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">secretguilddata_error</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">error</span><span class="p">):</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">error</span><span class="p">,</span> <span class="n">commands</span><span class="o">.</span><span class="n">CheckFailure</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s1">&#39;nothing to see here comrade.&#39;</span><span class="p">)</span>
</pre></div>
</div>
<p>If you want a more robust error system, you can derive from the exception and raise it instead of returning <code class="docutils literal notranslate"><span class="pre">False</span></code>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span> <span class="nc">NoPrivateMessages</span><span class="p">(</span><span class="n">commands</span><span class="o">.</span><span class="n">CheckFailure</span><span class="p">):</span>
<span class="k">pass</span>
<span class="k">def</span> <span class="nf">guild_only</span><span class="p">():</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">predicate</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="k">if</span> <span class="n">ctx</span><span class="o">.</span><span class="n">guild</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="k">raise</span> <span class="n">NoPrivateMessages</span><span class="p">(</span><span class="s1">&#39;Hey no DMs!&#39;</span><span class="p">)</span>
<span class="k">return</span> <span class="kc">True</span>
<span class="k">return</span> <span class="n">commands</span><span class="o">.</span><span class="n">check</span><span class="p">(</span><span class="n">predicate</span><span class="p">)</span>
<span class="nd">@guild_only</span><span class="p">()</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">test</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="s1">&#39;Hey this is not a DM! Nice.&#39;</span><span class="p">)</span>
<span class="nd">@test</span><span class="o">.</span><span class="n">error</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">test_error</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">error</span><span class="p">):</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">error</span><span class="p">,</span> <span class="n">NoPrivateMessages</span><span class="p">):</span>
<span class="k">await</span> <span class="n">ctx</span><span class="o">.</span><span class="n">send</span><span class="p">(</span><span class="n">error</span><span class="p">)</span>
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Since having a <code class="docutils literal notranslate"><span class="pre">guild_only</span></code> decorator is pretty common, it comes built-in via <a class="reference internal" href="api.html#discord.ext.commands.guild_only" title="discord.ext.commands.guild_only"><code class="xref py py-func docutils literal notranslate"><span class="pre">guild_only()</span></code></a>.</p>
</div>
<section id="global-checks">
<h3>Global Checks<a class="headerlink" href="#global-checks" title="Permalink to this headline"></a></h3>
<p>Sometimes we want to apply a check to <strong>every</strong> command, not just certain commands. The library supports this as well
using the global check concept.</p>
<p>Global checks work similarly to regular checks except they are registered with the <a class="reference internal" href="api.html#discord.ext.commands.Bot.check" title="discord.ext.commands.Bot.check"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Bot.check()</span></code></a> decorator.</p>
<p>For example, to block all DMs we could do the following:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@bot</span><span class="o">.</span><span class="n">check</span>
<span class="k">async</span> <span class="k">def</span> <span class="nf">globally_block_dms</span><span class="p">(</span><span class="n">ctx</span><span class="p">):</span>
<span class="k">return</span> <span class="n">ctx</span><span class="o">.</span><span class="n">guild</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span>
</pre></div>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>Be careful on how you write your global checks, as it could also lock you out of your own bot.</p>
</div>
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