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15.async.py
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86 lines (71 loc) · 2.47 KB
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# -*- coding: utf-8 -*-
"""
@author:XuMing（[email protected])
@description:
"""
def demo4():
"""
这是最终我们想要的实现.
"""
import asyncio # 引入 asyncio 库
async def washing1():
await asyncio.sleep(3) # 使用 asyncio.sleep(), 它返回的是一个可等待的对象
print('washer1 finished')
async def washing2():
await asyncio.sleep(2)
print('washer2 finished')
async def washing3():
await asyncio.sleep(5)
print('washer3 finished')
"""
事件循环机制分为以下几步骤:
1. 创建一个事件循环
2. 将异步函数加入事件队列
3. 执行事件队列, 直到最晚的一个事件被处理完毕后结束
4. 最后建议用 close() 方法关闭事件循环, 以彻底清理 loop 对象防止误用
"""
# 1. 创建一个事件循环
loop = asyncio.get_event_loop()
# 2. 将异步函数加入事件队列
tasks = [
washing1(),
washing2(),
washing3(),
]
# 3. 执行事件队列, 直到最晚的一个事件被处理完毕后结束
loop.run_until_complete(asyncio.wait(tasks))
"""
PS: 如果不满意想要 "多洗几遍", 可以多写几句:
loop.run_until_complete(asyncio.wait(tasks))
loop.run_until_complete(asyncio.wait(tasks))
loop.run_until_complete(asyncio.wait(tasks))
...
"""
# 4. 如果不再使用 loop, 建议养成良好关闭的习惯
# (有点类似于文件读写结束时的 close() 操作)
loop.close()
"""
最终的打印效果:
washer2 finished
washer1 finished
washer3 finished
elapsed time = 5.126561641693115
(毕竟切换线程也要有点耗时的)
说句题外话, 我看有的博主的加入事件队列是这样写的:
tasks = [
loop.create_task(washing1()),
loop.create_task(washing2()),
loop.create_task(washing3()),
]
运行的效果是一样的, 暂不清楚为什么他们这样做.
"""
if __name__ == '__main__':
# 为验证是否真的缩短了时间, 我们计个时
from time import time
start = time()
# demo1() # 需花费10秒
# demo2() # 会报错: RuntimeWarning: coroutine ... was never awaited
# demo3() # 会报错: RuntimeWarning: coroutine ... was never awaited
demo4() # 需花费5秒多一点点
end = time()
print('elapsed time = ' + str(end - start))