python - 委托(delegate)给 python 3.6+ asyncio 协程中的生成器

Question

在 python 3.3 中，我可以执行以下操作

def _gen():
    for i in range(3):
        yield i

def gen():
    yield from _gen()

for i in gen():
    print(i)

>>> 0
>>> 1
>>> 2

我可以在 python 3.6 asyncio 协程中做同样的事情吗？ (警告，人为的例子)

async def _gen():
    for i in range(3):
        yield await get_num(i) # get_num is a coroutine

async def gen():
    yield from _gen() # Syntax error!

for i in gen():
    print(i)

我需要将 gen 定义为

async def gen():
    async for i in _gen():
        yield i

但似乎应该有一种方法可以委托(delegate)给另一个协程，就像我们可以使用 yield from

Answer 1

由于 described in PEP 525 的原因，Python 3.6 不支持

yield from :

While it is theoretically possible to implement yield from support for asynchronous generators, it would require a serious redesign of the generators implementation.

yield from is also less critical for asynchronous generators, since there is no need provide a mechanism of implementing another coroutines protocol on top of coroutines. And to compose asynchronous generators a simple async for loop can be used:

async def g1():
    yield 1
    yield 2

async def g2():
    async for v in g1():
        yield v