concurrent.futures模块

1.concurrent.futures模块介绍

2.ThreadPoolExecutor线程池使用

3.ProcessPoolExecutor进程池使用

4.其他方法使用

1.concurrent.futures模块介绍

# 介绍
    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

# 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

2.ThreadPoolExecutor线程池使用

from concurrent.futures import ThreadPoolExecutor
import time
import random

def task(n):
    print(n)
    time.sleep(random.randint(1, 3))
    return n ** 2

if __name__ == '__main__':
    executor = ThreadPoolExecutor(max_workers=5)       # 最多5个线程
    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())

3.ProcessPoolExecutor进程池使用

from concurrent.futures import ProcessPoolExecutor
import os
import time
import 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)       # 最多3个进程
    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())

4.其他方法使用

# map方法使用
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())

tpool = ThreadPoolExecutor(max_workers=5) 
tpool.map(func, range(20))  # 注意map方法拿不到返回值

# 回调函数
import time
from concurrent.futures import ThreadPoolExecutor

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

# 回调函数
def call_back(m):
    print('结果是 %s' % m.result())

tpool = ThreadPoolExecutor(max_workers=5)
for i in range(20):
    tpool.submit(func, i).add_done_callback(call_back)