奇怪的错误与atrribute没有发现

Question

有一段代码从REPL运行时在Win 7

from multiprocessing import Process, Pool 
import time 
from urllib import request 

def millis(): 
    return int(round(time.time() * 1000)) 

def http_get(url): 
    start_time = millis() 
    result = {"url": url, "data": request.urlopen(url, timeout=5).read()[:100]} 
    print(url + " took " + str(millis() - start_time) + " ms") 
    return result 



start_time = millis() 
if __name__ == "__main__": 
    urls = ['http://www.google.com/', 'https://foursquare.com/', 'http://www.yahoo.com/', 'http://www.bing.com/', "https://www.yelp.com/"] 
    pool = Pool(processes=5) 
    results = pool.map(http_get, urls) 
    print("\nTotal took " + str(millis() - start_time) + " ms\n") 
    for result in results: 
    print(result) 

产生一个奇怪的错误和错误是

Traceback (most recent call last): 
    File "c:\python36\lib\multiprocessing\process.py", line 249, in _bootstrap 
    self.run() 
    File "c:\python36\lib\multiprocessing\process.py", line 93, in run 
    self._target(*self._args, **self._kwargs) 
    File "c:\python36\lib\multiprocessing\pool.py", line 108, in worker 
    task = get() 
    File "c:\python36\lib\multiprocessing\queues.py", line 345, in get 
    return _ForkingPickler.loads(res) 
AttributeError: Can't get attribute 'http_get' on <module '__main__' (built-in)> 

我不知道什么我我做错了。没有多处理它就像魅力

Answer 1

从multiprocessing documentation：

注意

该软件包内的功能要求__main__模块可由儿童导入。编程指南中介绍了这一点，但值得在此指出。这意味着一些示例（如multiprocessing.pool.Pool示例）在交互式解释器中不起作用。