19-多进程学习

• 多进程学习
  • 注意逗号
  • 注意使用进程池
  • 注意使用异步
  • 注意查看任务管理器，多进程是否跑起来

import multiprocessing
import time

'''
进程池、线程池的使用有四种方式：apply_async、apply、map_async、map。其中apply_async和map_async是异步的，也就是启动进程函数之后会继续执行
后续的代码不用等待进程函数返回。apply_async和map_async方式提供了一写获取进程函数状态的函数：ready()、successful()、get()。
'''

def func(msg):
    print('msg: ', msg)
    time.sleep(1)
    print('********')
    return 'func_return: %s' % msg


if __name__ == '__main__':
    '''
    # apply_async
    print('\n--------apply_async------------')
    pool = multiprocessing.Pool(processes=4)
    results = []
    for i in range(10):
        msg = 'hello world %d' % i
        result = pool.apply_async(func, (msg,))
        results.append(result)
    print('apply_async: 不堵塞')

    for i in results:
        i.wait()  # 等待进程函数执行完毕

    for i in results:
        if i.ready():  # 进程函数是否已经启动了
            if i.successful():  # 进程函数是否执行成功
                print(i.get())  # 进程函数返回值
    '''

    '''
    # apply
    print('\n--------apply------------')
    pool = multiprocessing.Pool(processes=4)
    results = []
    for i in range(10):
        msg = 'hello world %d' % i
        result = pool.apply(func, (msg,))
        results.append(result)
    print('apply: 阻塞')  # 执行完func才执行该句
    pool.close()
    pool.join()  # join语句要放在close之后
    print(results)
    '''

    '''
    # map
    print('\n--------map------------')
    args = [1, 2, 4, 5, 7, 8]
    pool = multiprocessing.Pool(processes=6)
    return_data = pool.map(func, args)
    print('阻塞')  # 执行完func才执行该句
    pool.close()
    pool.join()  # join语句要放在close之后
    print(return_data)
    '''

    # map_async
    print('\n--------map_async------------')
    pool = multiprocessing.Pool(processes=6)
    args = [1, 2, 4, 5, 7, 8]
    result = pool.map_async(func, args)
    print('ready: ', result.ready())
    print('不堵塞')
    result.wait()  # 等待所有进程函数执行完毕

    if result.ready():  # 进程函数是否已经启动了
        if result.successful():  # 进程函数是否执行成功
            print(result.get())  # 进程函数返回值