Why is discord.py not recognizing variables outside “on_message()”?

Question

My discord.py script gives me an unexpected error. It basically marks all the variables that I defined outside of async def on_message(): but used under that as "not defined".

Well, you could easily fix it by defining them under on_message() too. Which I tried. But then, here's the problem: The variables would be set back to what you defined each time a message is sent, even if you did add, like a line saying change it to another value if this hapens. (eg prefix, as you can see below in the code, I want to change the bot's prefix using a command called "changeprefix" and it works, HOWEVER when another message is sent with that prefix, it wouldn't recognize it; because the line defining the variable at the beginning ran again and it all got reset.

Is there a way else than just removing on_message() and using discord.ext.commands or something? I'm more familiar with the on-message() system, moreover I would change the whole script if I switch to it.

import discord

client = discord.Client()
token= "some nice token"
#defining here results in "UnboundLocalError: local variable 'prefix' referenced before assignment", in the first line using the variable defined here

@client.event

async def on_message(message):
     #defining here results variables being refreshed each time a message is sent

Answer 1

I believe what you are looking for is global here is a simple example on how to use it.

something = 1

@client.event
async def on_message(message):
    global something
    something = something + 1
    print(something) # 2 at first iteration

#outside of on_message
print(something) # 2 it is the same

In case you want to use it with prefix make it a dict with guild.id as key and the value is the prefix.

btw using commands would be much easier to do so.

NOTE: If you restart your bot you are going to lose this info

Answer 2

If I understood your question correctly you want a variable that will change it's value everytime a command is invoked, you can use a global variable (I don't recommend it) or a bot var. Also use commands.Bot so you can use the command system

bot = commands.Bot(command_prefix='.')

# Using a global variable
my_var = 'my value'

@bot.command()
async def foo(ctx, arg):
    global my_var
    my_var = arg
    await ctx.send(f"Changed `my_var` value to `arg`")

# Using a bot var
bot.my_var = 'my value'

@bot.command()
async def foo(ctx, arg):
    bot.my_var = arg
    await ctx.send(f"Changed `bot.my_var` value to `arg`")