Using a coroutine as decorator

Question

in this scenario:

async def foo(f):
    async def wrapper(*args, **kwargs):
        return f(*args, **kwargs)
    return wrapper

@foo
async def boo(*args, **kwa         


        

Answer 1

Here is an alternate approach using the decorator library (i.e. pip install decorator first):

import asyncio

import decorator


@decorator.decorator
async def decorate_coro(coro, *args, **kwargs):
    try:
        res = await coro(*args, **kwargs)
    except Exception as e:
        print(e)
    else:
        print(res)


@decorate_coro
async def f():
    return 42


@decorate_coro
async def g():
    return 1 / 0


async def main():
    return await asyncio.gather(f(), g())

if __name__ == '__main__':
    asyncio.run(main())

Output:

42
division by zero

Answer 2

Thanks to @blacknght's comment, considering

def foo():
    def wrapper(func):
        @functools.wraps(func)
        async def wrapped(*args):
             # Some fancy foo stuff
            return await func(*args)
        return wrapped
    return wrapper

and

def boo():
    def wrapper(func):
        @functools.wraps(func)
        async def wrapped(*args):
            # Some fancy boo stuff
            return await func(*args)
        return wrapped
    return wrapper

as two decorators, and

@foo()
@boo()
async def work(*args):
    pass

As the foo is wrapping the work coroutine, the key is to await the func(*arg) in both decorators.

Answer 3

def foo(f):
    async def wrapper(*args, **kwargs):
        return await f(*args, **kwargs)
    return wrapper

@foo
async def boo(*args, **kwargs):
    pass

Your decorator needs to be a normal function and it will work fine.

When a decorator is evaluated python executes the method with the function as the argument.

@foo
async def boo():
    pass

Evaluates to:

__main__.boo = foo(boo)

If foo is an async function type(main.boo) will be a coroutine object, not a function object. But if foo is a regular synch function it will evaluate right away and main.boo will be the wrapper returned.