Why is "guild" not defined such as in video? | discord.py

Question

I'm following a video on how to change prefixes server specific. I changed it to use channels instead but now I got the problem that the name guild is not defined. In the video the YouTuber has got no error. What am I doing wrong?

The Code:

@client.event
async def on_guild_join(guild):
    with open("welcomechanels.json", "r") as f:
        welcomechannels = json.load(f)
        
    welcomechannels[str(guild.id)] = ""

    with open("welcomechannels.json", "W"):
        json.dump(welcomechannels, f)

@client.command(name="setwelcomechannel")
@commands.has_permissions(administrator = True)
async def setwelcomechannel(ctx, channel: discord.Channel):
    with open("welcomechannels.json", "r") as f:
        welcomechannels = json.load(f)
        welcomechannels[str(guild.id)] = channel.id
        with open("welcomechannels.json", "w") as f:
            json.dump(welcomechannels, f)
    await ctx.send(f"Der Welcomechannel ist jetzt <#{channel.id}>.")

My Error:

His Code (https://youtu.be/Hh9MYiaV9U8?t=306):

UPDATE:

If someone joins the guild (server), I get this error:

Ignoring exception in on_member_join
Traceback (most recent call last):
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/client.py", line 343, in _run_event
    await coro(*args, **kwargs)
  File "main.py", line 78, in on_member_join
    await channel.send(f'<:899414480314859530:927212502654255125> Willkommen, {member.mention}')
AttributeError: 'NoneType' object has no attribute 'send'

The function on_member_join() looks like this:

@client.event
async def on_member_join(member):
        guild = member.guild
        channel = guild.get_channel(get_welcomechannel(client,member))
        e = discord.Embed(title=f"Willkommen in {guild.name}", colour=0xC0EEFF, description=
f'''
{member.mention}
<a:614619624268365829:915316001401344011> Schau doch gerne mal vorbei in... <a:614619624268365829:915316001401344011> 
<a:880584719916499055:927212502570369024> <#889211881661800529>
<a:880584719916499055:927212502570369024> <#889211881288499298>
<a:880584719916499055:927212502570369024> <#889211881661800533>
<a:880584719916499055:927212502570369024> <#889211881921867866>
<a:614619624268365829:915316001401344011>  Habt Spaß auf {guild.name} und seid aktiv!<a:614619624268365829:915316001401344011>
''')
        e.set_image(url='https://cdn.discordapp.com/attachments/748986660674601040/927204486307524608/6841391f576d4afcb2673b9dcc4d4dd1.gif')
        await channel.send(f'<:899414480314859530:927212502654255125> Willkommen, {member.mention}')
        await channel.send(embed=e)

The function get_welcomechannel() looks like this:

def get_welcomechannel(client, message):
    with open("./welcomechannels.json", "r") as f:
        welcomechannels = json.load(f)

    return welcomechannels[str(message.guild.id)]

I added the guild id and the channel id manually but I still can't change them with the command setwelcomechannel.

Answer 1

Just use ctx.guild. Guild isnt defined in your command because well... it doesn't know what guild is. You can use the .guild property of the ctx to get the guild it was in.

Also, instead of <#{channel.id}>, you can use the .mention property of a channel to to the same thing.

@client.event
async def on_guild_join(guild):
    with open("welcomechanels.json", "r") as f:
        welcomechannels = json.load(f)
        
    welcomechannels[str(guild.id)] = ""

    with open("welcomechannels.json", "W"):
        json.dump(welcomechannels, f)

@client.command(name="setwelcomechannel")
@commands.has_permissions(administrator = True)
async def setwelcomechannel(ctx, channel: discord.Channel):
    with open("welcomechannels.json", "r") as f:
        welcomechannels = json.load(f)
        welcomechannels[str(ctx.guild.id)] = channel.id
        with open("welcomechannels.json", "w") as f:
            json.dump(welcomechannels, f)
    await ctx.send(f"Der Welcomechannel ist jetzt {channel.mention}.")