python asyncio 获取协程返回值和使用callback
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())