如何在异步函数中使用"yield"?

编程入门行业动态更新时间:2024-10-25 00:36:47

本文介绍了如何在异步函数中使用"yield"?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！问题描述

我想使用生成器yield和async函数.我阅读了该主题，并编写了下一个代码:

I want to use generator yield and async functions. I read this topic, and wrote next code:

import asyncio async def createGenerator(): mylist = range(3) for i in mylist: await asyncio.sleep(1) yield i*i async def start(): mygenerator = await createGenerator() for i in mygenerator: print(i) loop = asyncio.get_event_loop() try: loop.run_until_complete(start()) except KeyboardInterrupt: loop.stop() pass

但是我得到了错误:

SyntaxError:异步函数中的'yield'

SyntaxError: 'yield' inside async function

如何在异步函数中使用良率生成器?

How to use yield generator in async function?

推荐答案

更新:

从Python 3.6开始，我们有了异步生成器，并且能够使用yield直接在协程内部.

Starting with Python 3.6 we have asynchronous generators and able to use yield directly inside coroutines.

import asyncio async def async_generator(): for i in range(3): await asyncio.sleep(1) yield i*i async def main(): async for i in async_generator(): print(i) loop = asyncio.get_event_loop() try: loop.run_until_complete(main()) finally: loop.run_until_complete(loop.shutdown_asyncgens()) # see: docs.python/3/library/asyncio-eventloop.html#asyncio.loop.shutdown_asyncgens loop.close()

Python 3.5的旧答案:

您不能在协程内部yield.唯一的方法是实现异步迭代器使用__aiter__/__anext__魔术方法手动进行.就您而言:

You can't yield inside coroutines. Only way is to implement Asynchronous Iterator manually using __aiter__/__anext__ magic methods. In your case:

import asyncio class async_generator: def __init__(self, stop): self.i = 0 self.stop = stop async def __aiter__(self): return self async def __anext__(self): i = self.i self.i += 1 if self.i <= self.stop: await asyncio.sleep(1) return i * i else: raise StopAsyncIteration async def main(): async for i in async_generator(3): print(i) if __name__ == "__main__": loop = asyncio.get_event_loop() loop.run_until_complete(main())

输出: