协程-asyncio模块

asyncio模块

启动单个协程

用法

• 必须要是协程方法async def demo():
• 阻塞前必须有await
• 必须创建事件循环loop = asyncio.get_event_loop()
• 任务执行必须加括号loop.run_until_complete(demo())

必须先创建一个事件循环：loop = asyncio.get_event_loop()

执行任务：loop.run_until_complete(demo())

import asyncio
# 启动一个任务
async def demo():   # 协程方法
    print('start')
    await asyncio.sleep(1)  # 阻塞
    print('end')

loop = asyncio.get_event_loop()  # 创建一个事件循环

loop.run_until_complete(demo())  # 把demo任务丢到事件循环中去执行

启动多个协程

启动多个任务,并且没有返回值

先创建事件循环loop = asyncio.get_event_loop()

增加一个wait对象wait_obj = asyncio.wait([demo(),demo(),demo()])

将wait对象丢到事件循环中去loop.run_until_complete(wait_obj)

import asyncio
# 启动多个任务,并且没有返回值
async def demo():   # 协程方法
    print('start')
    await asyncio.sleep(1)  # 阻塞
    print('end')

loop = asyncio.get_event_loop()  # 创建一个事件循环

wait_obj = asyncio.wait([demo(),demo(),demo()])

loop.run_until_complete(wait_obj)

启动多个任务并且有返回值

先创建事件循环loop = asyncio.get_event_loop()

创建任务对象

t1 = loop.create_task(demo())
t2 = loop.create_task(demo())
tasks = [t1,t2]

增加一个wait对象wait_obj = asyncio.wait(tasks)

将wait对象丢到事件循环中去loop.run_until_complete(wait_obj)

t.result()获取对应任务的返回值

async def demo():   # 协程方法
    print('start')
    await asyncio.sleep(1)  # 阻塞
    print('end')
    return 123

loop = asyncio.get_event_loop()
#
t1 = loop.create_task(demo())
t2 = loop.create_task(demo())
tasks = [t1,t2]
wait_obj = asyncio.wait([t1,t2])
#
loop.run_until_complete(wait_obj)
for t in tasks:
    print(t.result())

谁先回来先取谁的结果

创建main协程方法

# 谁先回来先取谁的结果
import asyncio
async def demo(i):   # 协程方法
    print('start')
    await asyncio.sleep(10-i)  # 阻塞
    print('end')
    return i,123

async def main():
    task_l = []
    for i in range(10):
        task = asyncio.ensure_future(demo(i))
        task_l.append(task)
    for ret in asyncio.as_completed(task_l):
        res = await ret
        print(res)

loop = asyncio.get_event_loop()
loop.run_until_complete(main())