Python之concurrent.futures

concurrent.futures

ProcessPoolExecutor

进程池，提供异步调用

基本方法

• submit(fn, args, *kwargs) 异步提交任务

• map(func, *iterables, timeout=None, chunksize=1) 取代for循环submit的操作

• shutdown(wait=True) 相当于进程池的pool.close()+pool.join()操作

  wait=True，等待池内所有任务执行完毕回收完资源后才继续
  wait=False，立即返回，并不会等待池内的任务执行完毕
  但不管wait参数为何值，整个程序都会等到所有任务执行完毕
  submit和map必须在shutdown之前

• result(timeout=None)取得结果

• add_done_callback(fn)回调函数

from concurrent.futures import ThreadPoolExecutor, ProcessPoolExecutor

import os, time, random


def task(n):
    print('%s is runing' % os.getpid())
    time.sleep(random.randint(1, 3))
    return n ** 2


if __name__ == '__main__':

    executor = ProcessPoolExecutor(max_workers=3)

    futures = []
    for i in range(11):
        future = executor.submit(task, i)
        futures.append(future)
    executor.shutdown(True)
    print('+++>')
    for future in futures:
        print(future.result())

ThreadPoolExecutor

线程池，提供异步调用，用法与ProcessPoolExecutor相同，只需要将ProcessPoolExecutor换成ThreadPoolExecutor

import time
from concurrent.futures import ThreadPoolExecutor


def func(n):
    time.sleep(2)
    print(n)
    return n * n


def call_back(m):
    print('结果是 %s' % m.result())


if __name__ == '__main__':
    tpool = ThreadPoolExecutor(max_workers=5)  # 默认 不要超过cpu个数*5
    for i in range(20):
        tpool.submit(func, i).add_done_callback(call_back)