如何将线程执行结果追加到response列表？当前添加的是None值

嘿，我来帮你搞定这个问题！你现在的代码里response.append(threads[-1].start())这行是关键问题——start()方法只是负责启动线程，它根本不会返回线程函数的执行结果，所以每次append进去的都是None，这就导致你的response列表全是None啦。

下面给你几种实用的解决方法，你可以根据自己的需求选：

方法1：给线程对象加自定义属性存结果 #

我们可以让线程函数把结果存在自己的线程对象里，等线程跑完再把结果取出来：

import requests
import threading

def URLOK(url, thread_obj):
    # 这里假设你已经定义好了proxies，没定义的话可以去掉这个参数
    page = requests.get(url, proxies=proxies)
    # 把结果赋值给线程对象的自定义属性result
    thread_obj.result = url + ":" + str(page.status_code) + "\n"

urls = ["http://www.google.com","http://www.amazon.com","http://www.amazon.ca","http://www.google.ca"]
response = []
threads = []

for url in urls:
    # 创建线程时把当前线程对象传进去
    t = threading.Thread(target=URLOK, kwargs={'url': url, 'thread_obj': threading.current_thread()})
    threads.append(t)
    t.start()

# 先等所有线程执行完毕
for t in threads:
    t.join()
    # 从线程对象里取出结果加到response里
    response.append(t.result)

# 打印结果
for res in response:
    print(res)

方法2：用线程安全的队列收集结果 #

队列天生就是线程安全的，非常适合多线程环境下传递数据，不用担心竞态问题：

import requests
import threading
import queue

def URLOK(url, result_queue):
    page = requests.get(url, proxies=proxies)
    # 把结果放进队列
    result_queue.put(url + ":" + str(page.status_code) + "\n")

urls = ["http://www.google.com","http://www.amazon.com","http://www.amazon.ca","http://www.google.ca"]
result_queue = queue.Queue()
threads = []

for url in urls:
    t = threading.Thread(target=URLOK, kwargs={'url': url, 'result_queue': result_queue})
    threads.append(t)
    t.start()

# 等待所有线程完成
for t in threads:
    t.join()

# 从队列里取出所有结果
response = []
while not result_queue.empty():
    response.append(result_queue.get())

for res in response:
    print(res)

方法3：用ThreadPoolExecutor（最简洁） #

如果你不想手动管理线程，Python标准库的concurrent.futures模块可以帮你一键搞定线程池和结果收集，代码超简洁：

import requests
from concurrent.futures import ThreadPoolExecutor

def URLOK(url):
    page = requests.get(url, proxies=proxies)
    return url + ":" + str(page.status_code) + "\n"

urls = ["http://www.google.com","http://www.amazon.com","http://www.amazon.ca","http://www.google.ca"]

# 用线程池自动处理线程和结果
with ThreadPoolExecutor() as executor:
    # executor.map会自动把每个url传给URLOK，返回结果列表
    response = list(executor.map(URLOK, urls))

for res in response:
    print(res)

内容的提问来源于stack exchange，提问作者Tronald Dump