Event Loop Internals

Preview — 3 of 10 questions

What is the output of the following code?

javascript

async def simple():
    return 42

coro = simple()
try:
    coro.send(None)
except StopIteration as e:
    print(e.value)

ANone

B42

CThe program hangs, since .send(None) never returns.

DTypeError: coroutine.send() takes 0 positional arguments

What is the output of the following code?

javascript

import asyncio

class Later:
    def __await__(self):
        yield
        return "value from Later"

async def main():
    result = await Later()
    print(result)

asyncio.run(main())

ATypeError: object Later can't be used in 'await' expression

BNone

Cvalue from Later

D<generator object Later.__await__ at 0x...>

Which statement correctly describes running asyncio event loops across multiple OS threads?

AOnly the main thread of a Python process is ever allowed to run an event loop; no other thread can run one at all.

BA single asyncio event loop can be freely shared and driven simultaneously by multiple threads without any special handling.

Casyncio automatically creates a new hidden event loop for every coroutine call, regardless of thread.

DEach OS thread that wants to run asyncio coroutines needs its own separate event loop — a single event loop instance is tied to the thread running it and cannot be safely driven concurrently from multiple threads at once.

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