• python 进程池、线程池 与异步调用、回调机制


    进程池、线程池使用案例

    from concurrent.futures import ProcessPoolExecutor  # 进程池模块
    from concurrent.futures import ThreadPoolExecutor  # 线程池模块
    import os, time, random
    
    #  下面是以进程池为例, 线程池只是模块改一下即可
    def talk(name):
        print('name: %s  pis%s  run' % (name,os.getpid()))
        time.sleep(random.randint(1, 3))
    
    if __name__ == '__main__':
        pool = ProcessPoolExecutor(4)  # 设置线程池大小,默认等于cpu核数
        for i in range(10):
            pool.submit(talk, '进程%s' % i)  # 异步提交(只是提交需要运行的线程不等待)
    
        # 作用1:关闭进程池入口不能再提交了   作用2:相当于jion 等待进程池全部运行完毕
        pool.shutdown(wait=True)  
        print('主进程')

    异步调用与同步调用

    concurrent.futures模块提供了高度封装的异步调用接口
    ThreadPoolExecutor:线程池,提供异步调用
    ProcessPoolExecutor: 进程池,提供异步调用

    • 同步调用

    from concurrent.futures import ProcessPoolExecutor  # 进程池模块
    import os, time, random
    
    
    # 1、同步调用: 提交完任务后、就原地等待任务执行完毕,拿到结果,再执行下一行代码(导致程序串行执行)
    def talk(name):
        print('name: %s  pis%s  run' % (name,os.getpid()))
        time.sleep(random.randint(1, 3))
    
    if __name__ == '__main__':
        pool = ProcessPoolExecutor(4)
        for i in range(10):
            pool.submit(talk, '进程%s' % i).result()  # 同步迪奥用,result(),相当于join 串行
    
        pool.shutdown(wait=True)
        print('主进程')

    • 异步调用

    from concurrent.futures import ProcessPoolExecutor  # 进程池模块
    import os, time, random
    
    def talk(name):
        print('name: %s  pis%s  run' % (name,os.getpid()))
        time.sleep(random.randint(1, 3))
    
    if __name__ == '__main__':
        pool = ProcessPoolExecutor(4)
        for i in range(10):
            pool.submit(talk, '进程%s' % i)  # 异步调用,不需要等待
    
        pool.shutdown(wait=True)
        print('主进程')

    回调机制

    可以为进程池或线程池内的每个进程或线程绑定一个函数,该函数在进程或线程的任务执行完毕后自动触发,并接收任务的返回值当作参数,该函数称为回调函数

    #parse_page拿到的是一个future对象obj,需要用obj.result()拿到结果
    p.submit(这里异步调用).add_done_callback(方法)

    • 案例:下载解析网页页面
    import time
    import requests
    from concurrent.futures import ThreadPoolExecutor  # 线程池模块
    
    def get(url):
        print('GET %s' % url)
        response = requests.get(url)  # 下载页面
        time.sleep(3)  # 模拟网络延时
        return {'url': url, 'content': response.text}  # 页面地址和页面内容
    
    def parse(res):
        res = res.result()  # !取到res结果 【回调函数】带参数需要这样
        print('%s res is %s' % (res['url'], len(res['content'])))
    
    if __name__ == '__main__':
        urls = {
            'http://www.baidu.com',
            'http://www.360.com',
            'http://www.iqiyi.com'
        }
    
        pool = ThreadPoolExecutor(2)
        for i in urls:
            pool.submit(get, i).add_done_callback(parse)  # 【回调函数】执行完线程后,跟一个函数 
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  • 原文地址:https://www.cnblogs.com/geogre123/p/11325841.html
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