Python并发.futures : threads don't start

Question

我制作了一个程序，使用并发.futures 启动 4 个线程并向列表中的每个网站发送请求。

问题:它无法启动

import requests
import threading
import concurrent.futures

list=['amazon.com', 'google.com', 'youtube.com', 'microsoft.com']

def start(url):
    requests.get('https://'+url)
    print(line+' finished')

with concurrent.futures.ThreadPoolExecutor(max_workers=4) as executor:
    for url in list:
        executor.submit(start, url)

另一方面，这有效:

import concurrent.futures

def start():
    print('lol')

with concurrent.futures.ThreadPoolExecutor(max_workers=4) as executor:
    for i in range(10):
        executor.submit(start)

Answer 1

您刚刚安排了任务，但没有等待结果，并且代码中出现错误(使用 undefined variable )，但错误消息已被上下文管理器“吞没”。

executor.submit方法返回 Future对象，您可以通过调用 result 获取返回值方法:

import requests
import threading
import concurrent.futures

URLS = ['amazon.com', 'google.com', 'youtube.com', 'microsoft.com']


def start(url):
    requests.get('https://' + url)
    print(f'{url}: finished')


def main():
    futures = []

    with concurrent.futures.ThreadPoolExecutor(max_workers=4) as executor:
        for url in URLS:
            futures.append(executor.submit(start, url))

        for future in futures:
            future.result()


if __name__ == "__main__":
    main()