00164 Python concurrent 包学习笔记

Python 多线程多进程全局解释器锁（GIL）

Python

发布日期: 2024-08-29

更新日期: 2024-12-28

前言

concurrent 包，目前，此包中只有一个模块：

concurrent.futures —— 启动并行任务

concurrent.futures 模块提供异步执行可调用对象高层接口。

异步执行可以由 ThreadPoolExecutor 使用线程或由 ProcessPoolExecutor 使用单独的进程来实现。两者都是实现抽象类 Executor 定义的接口。

操作系统：Windows 11 家庭中文版

参考文档

ThreadPoolExecutor

ThreadPoolExecutor 是 Executor 的子类，它使用线程池来异步执行调用。

import concurrent.futures
import urllib.request

URLS = ['http://www.foxnews.com/',
        'http://www.cnn.com/',
        'http://europe.wsj.com/',
        'http://www.bbc.co.uk/',
        'http://nonexistant-subdomain.python.org/']

# Retrieve a single page and report the URL and contents
def load_url(url, timeout):
    with urllib.request.urlopen(url, timeout=timeout) as conn:
        return conn.read()

# We can use a with statement to ensure threads are cleaned up promptly
with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
    # Start the load operations and mark each future with its URL
    future_to_url = {executor.submit(load_url, url, 60): url for url in URLS}
    for future in concurrent.futures.as_completed(future_to_url):
        url = future_to_url[future]
        try:
            data = future.result()
        except Exception as exc:
            print('%r generated an exception: %s' % (url, exc))
        else:
            print('%r page is %d bytes' % (url, len(data)))

ProcessPoolExecutor

ProcessPoolExecutor 类是 Executor 的子类，它使用进程池来异步地执行调用。 ProcessPoolExecutor 会使用 multiprocessing 模块，这允许它绕过全局解释器锁但也意味着只可以处理和返回可封存的对象。

__main__ 模块必须可以被工作者子进程导入。这意味着 ProcessPoolExecutor 不可以工作在交互式解释器中。

import concurrent.futures
import math

PRIMES = [
    112272535095293,
    112582705942171,
    112272535095293,
    115280095190773,
    115797848077099,
    1099726899285419]

def is_prime(n):
    if n < 2:
        return False
    if n == 2:
        return True
    if n % 2 == 0:
        return False

    sqrt_n = int(math.floor(math.sqrt(n)))
    for i in range(3, sqrt_n + 1, 2):
        if n % i == 0:
            return False
    return True

def main():
    with concurrent.futures.ProcessPoolExecutor() as executor:
        for number, prime in zip(PRIMES, executor.map(is_prime, PRIMES)):
            print('%d is prime: %s' % (number, prime))

if __name__ == '__main__':
    main()