Modernize code to use f-strings

This also removes the encoding on the top, since Python 3 does it by
default. It also changes some methods to use `yield from`.

examples/basic_bot.py

@@ -61,7 +61,7 @@ async def cool(ctx):
     In reality this just checks if a subcommand is being invoked.
     """
     if ctx.invoked_subcommand is None:
-        await ctx.send('No, {0.subcommand_passed} is not cool'.format(ctx))
+        await ctx.send(f'No, {ctx.subcommand_passed} is not cool')
 
 @cool.command(name='bot')
 async def _bot(ctx):

examples/basic_voice.py

@@ -70,9 +70,9 @@ class Music(commands.Cog):
         """Plays a file from the local filesystem"""
 
         source = discord.PCMVolumeTransformer(discord.FFmpegPCMAudio(query))
-        ctx.voice_client.play(source, after=lambda e: print('Player error: %s' % e) if e else None)
+        ctx.voice_client.play(source, after=lambda e: print(f'Player error: {e}') if e else None)
 
-        await ctx.send('Now playing: {}'.format(query))
+        await ctx.send(f'Now playing: {query}')
 
     @commands.command()
     async def yt(self, ctx, *, url):
@@ -80,9 +80,9 @@ class Music(commands.Cog):
 
         async with ctx.typing():
             player = await YTDLSource.from_url(url, loop=self.bot.loop)
-            ctx.voice_client.play(player, after=lambda e: print('Player error: %s' % e) if e else None)
+            ctx.voice_client.play(player, after=lambda e: print(f'Player error: {e}') if e else None)
 
-        await ctx.send('Now playing: {}'.format(player.title))
+        await ctx.send(f'Now playing: {player.title}')
 
     @commands.command()
     async def stream(self, ctx, *, url):
@@ -90,9 +90,9 @@ class Music(commands.Cog):
 
         async with ctx.typing():
             player = await YTDLSource.from_url(url, loop=self.bot.loop, stream=True)
-            ctx.voice_client.play(player, after=lambda e: print('Player error: %s' % e) if e else None)
+            ctx.voice_client.play(player, after=lambda e: print(f'Player error: {e}') if e else None)
 
-        await ctx.send('Now playing: {}'.format(player.title))
+        await ctx.send(f'Now playing: {player.title}')
 
     @commands.command()
     async def volume(self, ctx, volume: int):
@@ -102,7 +102,7 @@ class Music(commands.Cog):
             return await ctx.send("Not connected to a voice channel.")
 
         ctx.voice_client.source.volume = volume / 100
-        await ctx.send("Changed volume to {}%".format(volume))
+        await ctx.send(f"Changed volume to {volume}%")
 
     @commands.command()
     async def stop(self, ctx):

examples/converters.py

@@ -29,7 +29,7 @@ async def userinfo(ctx: commands.Context, user: discord.User):
     user_id = user.id
     username = user.name
     avatar = user.avatar_url
-    await ctx.send('User found: {} -- {}\n{}'.format(user_id, username, avatar))
+    await ctx.send(f'User found: {user_id} -- {username}\n{avatar}')
 
 @userinfo.error
 async def userinfo_error(ctx: commands.Context, error: commands.CommandError):
@@ -70,7 +70,7 @@ class ChannelOrMemberConverter(commands.Converter):
         # If the value could not be converted we can raise an error
         # so our error handlers can deal with it in one place.
         # The error has to be CommandError derived, so BadArgument works fine here.
-        raise commands.BadArgument('No Member or TextChannel could be converted from "{}"'.format(argument))
+        raise commands.BadArgument(f'No Member or TextChannel could be converted from "{argument}"')
 
 
 
@@ -81,7 +81,7 @@ async def notify(ctx: commands.Context, target: ChannelOrMemberConverter):
     # the `argument` parameter of the `ChannelOrMemberConverter.convert` method and 
     # the conversion will go through the process defined there.
 
-    await target.send('Hello, {}!'.format(target.name))
+    await target.send(f'Hello, {target.name}!')
 
 @bot.command()
 async def ignore(ctx: commands.Context, target: typing.Union[discord.Member, discord.TextChannel]):
@@ -95,9 +95,9 @@ async def ignore(ctx: commands.Context, target: typing.Union[discord.Member, dis
 
     # To check the resulting type, `isinstance` is used
     if isinstance(target, discord.Member):
-        await ctx.send('Member found: {}, adding them to the ignore list.'.format(target.mention))
+        await ctx.send(f'Member found: {target.mention}, adding them to the ignore list.')
     elif isinstance(target, discord.TextChannel): # this could be an `else` but for completeness' sake.
-        await ctx.send('Channel found: {}, adding it to the ignore list.'.format(target.mention))
+        await ctx.send(f'Channel found: {target.mention}, adding it to the ignore list.')
 
 # Built-in type converters.
 @bot.command()

examples/guessing_game.py

@@ -25,12 +25,12 @@ class MyClient(discord.Client):
             try:
                 guess = await self.wait_for('message', check=is_correct, timeout=5.0)
             except asyncio.TimeoutError:
-                return await message.channel.send('Sorry, you took too long it was {}.'.format(answer))
+                return await message.channel.send(f'Sorry, you took too long it was {answer}.')
 
             if int(guess.content) == answer:
                 await message.channel.send('You are right!')
             else:
-                await message.channel.send('Oops. It is actually {}.'.format(answer))
+                await message.channel.send(f'Oops. It is actually {answer}.')
 
 client = MyClient()
 client.run('token')

examples/new_member.py

@@ -12,7 +12,7 @@ class MyClient(discord.Client):
     async def on_member_join(self, member):
         guild = member.guild
         if guild.system_channel is not None:
-            to_send = 'Welcome {0.mention} to {1.name}!'.format(member, guild)
+            to_send = f'Welcome {member.mention} to {guild.name}!'
             await guild.system_channel.send(to_send)