python 将进程池放在装饰器里为什么不生效也没报错

草帽路飞UU

我想把进程池封装在装饰器里，但是它既没生效也没报错

1. def handle_request(response):
   
2.     print str(response)
   
3. 
   
4. def run_in_process(process_num):
   
5.     def _run_in_process(f):
   
6.         def __run_in_process(*args, **kwargs):
   
7.             pool = multiprocessing.Pool(processes=process_num)
   
8.             for i in range(process_num):
   
9.                 pool.apply_async(f, args=args, kwds=kwargs, callback=kwargs.get("callback"))
   
10.             pool.close()
    
11.             pool.join()
    
12. 
    
13.         return __run_in_process
    
14. 
    
15.     return _run_in_process
    
16. 
    
17. 
    
18. @run_in_process(process_num)
    
19. def main():
    
20.     http_client = AsyncHTTPClient()
    
21.     http_client.fetch(url, callback=handle_request)
    
22.     global loop
    
23.     loop = tornado.ioloop.IOLoop.instance()
    
24.     if loop._running is False:
    
25.         loop.start()

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结果如下：

1. /usr/bin/python2.7 /home/workspace/py_project/crawler/center/sample.py
   
2. 
   
3. Process finished with exit code 0

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但是奇怪的是，我用多进程的方式重写一次，发现是可以生效的

1. def handle_request(response):
   
2.     print str(response)
   
3. 
   
4. def run_in_process(process_num):
   
5.     def _run_in_process(f):
   
6.         def __run_in_process(*args, **kwargs):
   
7.             _processes = []
   
8.             for i in xrange(process_num):
   
9.                 p = multiprocessing.Process(target=f, args=args, kwargs=kwargs)
   
10.                 p.start()
    
11.                 _processes.append(p)
    
12. 
    
13.             for p in _processes:
    
14.                 p.join()
    
15. 
    
16.         return __run_in_process
    
17.     return _run_in_process
    
18. 
    
19. 
    
20. @run_in_process(process_num)
    
21. def main():
    
22.     http_client = AsyncHTTPClient()
    
23.     http_client.fetch(url, callback=handle_request)
    
24.     global loop
    
25.     loop = tornado.ioloop.IOLoop.instance()
    
26.     if loop._running is False:
    
27.         loop.start()
    
28. 
    
29. 
    
30. if __name__ == '__main__':
    
31.     main()
    

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日志如下

1. /usr/bin/python2.7 /home/workspace/py_project/crawler/center/sample.py
   
2. HTTPResponse(_body=None,buffer=<_io.BytesIO object at 0x7f2fdaa21ef0>,code=200,effective_url='http://www.baidu.com',error=None,headers=<tornado.httputil.HTTPHeaders object at 0x7f2fdaa425d0>,reason='OK',request=<tornado.httpclient.HTTPRequest object at 0x7f2fdaa42250>,request_time=0.014312028884887695,time_info={})
   
3. HTTPResponse(_body=None,buffer=<_io.BytesIO object at 0x7f2fdaa21ef0>,code=200,effective_url='http://www.baidu.com',error=None,headers=<tornado.httputil.HTTPHeaders object at 0x7f2fdaa43450>,reason='OK',request=<tornado.httpclient.HTTPRequest object at 0x7f2fdaa430d0>,request_time=0.02327895164489746,time_info={})
   
4. HTTPResponse(_body=None,buffer=<_io.BytesIO object at 0x7f2fdaa21ef0>,code=200,effective_url='http://www.baidu.com',error=None,headers=<tornado.httputil.HTTPHeaders object at 0x7f2fdaa43510>,reason='OK',request=<tornado.httpclient.HTTPRequest object at 0x7f2fdaa43190>,request_time=0.026951074600219727,time_info={})
   
5. HTTPResponse(_body=None,buffer=<_io.BytesIO object at 0x7f2fdaa21ef0>,code=200,effective_url='http://www.baidu.com',error=None,headers=<tornado.httputil.HTTPHeaders object at 0x7f2fdaa42690>,reason='OK',request=<tornado.httpclient.HTTPRequest object at 0x7f2fdaa42310>,request_time=0.0552978515625,time_info={})
   
6. HTTPResponse(_body=None,buffer=<_io.BytesIO object at 0x7f2fdaa24ef0>,code=200,effective_url='http://www.baidu.com',error=None,headers=<tornado.httputil.HTTPHeaders object at 0x7f2fdaa39e10>,reason='OK',request=<tornado.httpclient.HTTPRequest object at 0x7f2fdaa39a90>,request_time=0.05612993240356445,time_info={})

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同样的情况也会出现在线程池跟协程的使用上，有谁知道这是怎么回事吗？

八戒你干嘛

同问，等大神来解答