Exec run async function

Question

I know that I shouldn't use exec because it's insecure but the code it run comes from the same file and is a string. How can I use exec to run an async function? It always returns me SyntaxError: 'await' outside function if I try it.

Edit: This is the Code where I am using exec:

async def command_processor(guild):
    while True:
        commands = {"[1] - Bot Permissions abrufen" : "print_permissions(guild)",
                    "Derzeit nicht verwendbar - [2] - Invite zu Gilde erstellen (max Nutzungen pro Invite: 1)" : "await print_invite(guild)",
                    "[3] - Gebannte Benutzer auflisten (benötigt Berechtigung {Mitglieder bannen}" : "print_banned(guild)",
                    "[4] - Ausgewählten Server wechseln" : "change_guild()",
                    "[5] - Ausgewählten Bot wechseln" : "change_bot()",
                    "[6] - Beenden" : "sys.exit()"
            }
        print("\n\n--------------- Befehle ---------------\n")
        for i in range(len(commands.keys())):
            print(list(commands.keys())[i])
        sel = input()
        print()
        try:
            int(sel)
        except:
            print("Bitte hier nur die Zahl eingeben")
        if int(sel) in range(len(commands.keys())):
            exec(list(commands.values())[int(sel)-1])

Out of curiosity, if the code comes from the same file, why does it need to be a string? Why can't it just be code? (An example in the question might help.) — 0x5453
– 0x5453, Commented Jan 6, 2021 at 13:45
It's just so that I can extend it more easily, because I have a dictionary with the Description what will be printed as the key and the command that will run as the value. — Moondancer
– Moondancer, Commented Jan 6, 2021 at 13:49
No, you have strings as values. You could just have the methods as values: {'1. Exit': sys.exit}. Then you can do list(commands.values())[int(sel)-1])() later on. — obeq
– obeq, Commented Jan 6, 2021 at 14:00

obeq · Accepted Answer · 2021-01-06 15:04:56Z

You could do this, I think. The problem with exec is that it doesn't return anything, so you would need to use eval instead. I think this could work:

async def command_processor(guild):
    while True:
        commands = {"[1] - Bot Permissions abrufen" : "print_permissions(guild)",
                    "Derzeit nicht verwendbar - [2] - Invite zu Gilde erstellen (max Nutzungen pro Invite: 1)" : "await print_invite(guild)",
                    "[3] - Gebannte Benutzer auflisten (benötigt Berechtigung {Mitglieder bannen}" : "print_banned(guild)",
                    "[4] - Ausgewählten Server wechseln" : "change_guild()",
                    "[5] - Ausgewählten Bot wechseln" : "change_bot()",
                    "[6] - Beenden" : "sys.exit()"
            }

# ...

        if int(sel) in range(len(commands.keys())):
            await eval(list(commands.values())[int(sel)-1])

But there's no need to use eval here, and you have a lot to lose. A simple way could be to use a dict, something along the lines:

commands = {1: {"description": "[1] - Bot Permission abrufen", "command" : print_permissions, "args": [guild]},
# ...
}

for cmd in commands:
    print(cmd['description'])

# ...
selected_command = commands[sel]
await selected_command['command'](*selected_command['args'])

But it gets tricky, since sometimes you have a coroutine and sometimes a regular method. To get around that, I guess you could do this:

commands = {
    1: {"description": "[1] - Bot Permission abrufen", "exec" : print_permissions, "args": [guild]},
    2: {"description": "Derzeit nicht verwendbar - [2] - Invite zu Gilde erstellen (max Nutzungen pro Invite: 1)", "exec": print_invite, "args": [guild]},
# ...
}

for cmd in commands:
    print(cmd['description'])

# ...
selected_command = commands[sel]
if asyncio.iscoroutinefunction(selected_command['exec']):
    await selected_command['exec'](*selected_command['args'])
else:
    selected_command['exec'](*selected_command['args'])

On a final note: It make's me nervous that we now have the key that needs to pressed in two different places. This will lead to tears in the end, mark my words. I would do something like this:

commands = [
    {
        "description": "[{keynum}] - Bot Permission abrufen",
        "exec" : print_permissions, "args": [guild]
    },
    {
        "description": "Derzeit nicht verwendbar - [{keynum}] - Invite zu Gilde erstellen (max Nutzungen pro Invite: 1)",
        "exec": print_invite, "args": [guild]
    },
]

for keynum, command in enumerate(commands):
    print(command['description'].format(keynum=keynum))

I haven't tested that code, so there's probably a bug, but you get the idea.

I just got this error TypeError: print_invite() argument after * must be an iterable, not Guild of the line selected_command['command'](*selected_command['args'])

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