Python小知识 - asyncio使用记录（1）

asyncio是什么，如何使用

官方介绍如下，熟读

asyncio is a library to write concurrent code using the async/await syntax.

asyncio is used as a foundation for multiple Python asynchronous frameworks that provide high-performance network and web-servers, database connection libraries, distributed task queues, etc.

asyncio is often a perfect fit for IO-bound and high-level structured network code.

asyncio provides a set of high-level APIs to:

run Python coroutines concurrently and have full control over their execution;

perform network IO and IPC;

control subprocesses;

distribute tasks via queues;

synchronize concurrent code;

Additionally, there are low-level APIs for library and framework developers to:

create and manage event loops, which provide asynchronous APIs for networking, running subprocesses, handling OS signals, etc;

implement efficient protocols using transports;

bridge callback-based libraries and code with async/await syntax.

简单的看下如何使用，建议使用 Python 3.7+

import asyncio


async def main():
    print("Print ..... 1")
    await asyncio.sleep(10)
    print("Print ..... 2")


asyncio.run(main())

运行下之后，可以发现，“Print ..... 1”输出之后要过10秒才会输出“Print ..... 2”

这个不是并发的吗，为什么，用起来却不是并发的

其实上面的代码只是展示了如何用asyncio的async/await语法

看下如何实现并发的操作

实现之前先看下我么要做的功能

import time
import asyncio


async def start_run(delay, name):
    await asyncio.sleep(delay)
    print('%s start run' % name)


async def main():
    print(f"started at {time.strftime('%X')}")

    await start_run(2, 'dog')
    await start_run(3, 'cat')

    print(f"finished at {time.strftime('%X')}")


asyncio.run(main())

运行后输出结果如下

started at 20:15:09
dog start run
cat start run
finished at 20:15:14

这里我们知道要如何运行了，下面我们来实现下如何并发

import time
import asyncio


async def start_run(delay, name):
    await asyncio.sleep(delay)
    print('%s start run' % name)


async def main():
    dog_run = asyncio.create_task(start_run(2, 'dog'))
    cat_run = asyncio.create_task(start_run(3, 'cat'))

    print(f"started at {time.strftime('%X')}")

    await dog_run
    await cat_run

    print(f"finished at {time.strftime('%X')}")


asyncio.run(main())

运行后输出结果如下

started at 20:19:18
dog start run
cat start run
finished at 20:19:23

提示：暂时别像下面这样操作

import time
import asyncio


async def start_run(delay, name):
    await asyncio.sleep(delay)
    print('%s start run' % name)


async def main():
    print(f"started at {time.strftime('%X')}")

    await asyncio.create_task(start_run(2, 'dog'))
    await asyncio.create_task(start_run(3, 'cat'))

    print(f"finished at {time.strftime('%X')}")


asyncio.run(main())

我实验了下，不会有效果，待查

Python小知识 - asyncio使用记录（1）

版权声明