CODEWITHSUNDEEP
asynchronousasync-awaitpython-3.5
MAA
MAA

Reputation: 1355

Can't await work on a computation other than functions in python3.5?

Does it have to be a function we are not blocking ? Why isn't this working?

async def trivial(L):
    await [num**2 for num in L]

So "Object list can't be used in 'await' expression", Am I correct in assuming it's only looking for a function or is there something that's possible to await??

Upvotes: 0

Views: 455

Answers (1)

jonrsharpe
jonrsharpe

Reputation: 122088

Per the documentation, await will:

Suspend the execution of coroutine on an awaitable object.

You're in a coroutine, but a list is not awaitable, it isn't "a coroutine or an object with an __await__() method."

Note that the list comprehension is fully evaluated, resulting in a list, before it gets passed to await, so there's no work left to be done at that point anyway. If you were doing something more complex than num**2 inside the loop, you could consider rewriting the process as an "asynchronous iterator" and using async for, as follows:

async def trivial(L):
    result = []
    async for item in process(L):
        result.apend(item)

This would allow other pending tasks to be run between iterations of your process over L.

Upvotes: 1

Related Questions