如何异步映射/过滤异步迭代？

Question

假设我有一个可以传递的异步迭代,async for然后如何将它映射并过滤到新的异步迭代器？以下代码是对我如何使用同步迭代执行相同操作的修改不起作用,因为s中yield不允许这样做async def.

async def mapfilter(aiterable, p, func):
    async for payload in aiterable:
        if p(payload):

            # This part isn't allowed, but hopefully it should be clear
            # what I'm trying to accomplish.
            yield func(payload)

Answer 1

一个最近公布的PEP草案(PEP 525) ,其支持定为Python 3.6,建议允许异步发电机与你想出了相同的语法.

同时,如果您不想处理异步迭代器样板,也可以在其注释asyncio_extras中使用CryingCyclops提到的库.

来自文档:

@async_generator
async def mygenerator(websites):
    for website in websites:
        page = await http_fetch(website)
        await yield_async(page)

async def fetch_pages():
    websites = ('http://foo.bar', 'http://example.org')
    async for sanitized_page in mygenerator(websites):
        print(sanitized_page)

还有async_generator库支持yield from构造.

Answer 2

名字不好的第 3 方库为异步迭代asyncstdlib提供了过滤器和映射。