python asyncio 获取协程返回值和使用callback

Reference from: https://www.cnblogs.com/callyblog/p/11216961.html

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())