python asyncio 获取协程返回值和使用callback

清疚 2021-10-29 13:16 775阅读 0赞

1. 获取协程返回值，实质就是future中的task

import asyncio
    import time
    async def get_html(url):
        print("start get url")
        await asyncio.sleep(2)
        return "bobby"
    
    def callback(url, future):
        print(url)
        print("send email to bobby")
    
    if __name__ == "__main__":
        start_time = time.time()
        loop = asyncio.get_event_loop()
        get_future = asyncio.ensure_future(get_html("http://www.imooc.com")) # 相当于开启一个future
        loop.run_until_complete(get_future) # 事件循环
        print(get_future.result()) # 获取结果

2. 使用loop自带的create task， 获取返回值

# 获取协程的返回值
    import asyncio
    import time
    from functools import partial
    async def get_html(url):
        print("start get url")
        await asyncio.sleep(2)
        return "bobby"
    
    def callback(url, future):
        print(url)
        print("send email to bobby")
    
    if __name__ == "__main__":
        start_time = time.time()
        loop = asyncio.get_event_loop()
        task = loop.create_task(get_html("http://www.imooc.com"))
        loop.run_until_complete(task)
        print(task.result())

3. 使用callback,只要await地方的内容一运行完，就会运行callback

# 获取协程的返回值
    import asyncio
    import time
    from functools import partial
    async def get_html(url):
        print("start get url")
        await asyncio.sleep(2)
        return "bobby"
    
    def callback(future): #这里默认传入一个future对象
        print("send email to bobby")
    
    if __name__ == "__main__":
        start_time = time.time()
        loop = asyncio.get_event_loop()
        task = loop.create_task(get_html("http://www.imooc.com"))
        task.add_done_callback(callback)
        loop.run_until_complete(task)
        print(task.result())

使用partial这个模块向callback函数中传入值

# 获取协程的返回值
    import asyncio
    import time
    from functools import partial
    async def get_html(url):
        print("start get url")
        await asyncio.sleep(2)
        return "bobby"
    
    def callback(future):
        print("send email to bobby")
    
    def callback1(url, future): # 传入值的时候，future必须在最后一个
        print(url)
        print("send email to bobby")
    if __name__ == "__main__":
        start_time = time.time()
        loop = asyncio.get_event_loop()
        task = loop.create_task(get_html("http://www.imooc.com"))
        task.add_done_callback(partial(callback1, "http://www.imooc.com"))
        loop.run_until_complete(task)
        print(task.result())

转载于:https://www.cnblogs.com/callyblog/p/11216961.html