Python3爬虫（十二） 爬虫性能

 Infi-chu:

http://www.cnblogs.com/Infi-chu/

一、简单的循环串行
一个一个循环，耗时是最长的，是所有的时间综合

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import requests url_list = [     'http://www.baidu.com',     'http://www.pythonsite.com',     'http://www.cnblogs.com/' ]   for url in url_list:     result = requests.get(url)     print(result.text)

二、通过线程池
整体耗时是所有连接里耗时最久的那个，相对于循环来说快了不少

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import requests from concurrent.futures import ThreadPoolExecutor   def fetch_request(url):     result = requests.get(url)     print(result.text)   url_list = [     'http://www.baidu.com',     'http://www.bing.com',     'http://www.cnblogs.com/' ] pool = ThreadPoolExecutor(10)   for url in url_list:     #去线程池中获取一个线程，线程去执行fetch_request方法     pool.submit(fetch_request,url)   pool.shutdown(True)

三、线程池+回调函数
定义了一个回调函数

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from concurrent.futures import ThreadPoolExecutor import requests     def fetch_async(url):     response = requests.get(url)       return response     def callback(future):     print(future.result().text)     url_list = [     'http://www.baidu.com',     'http://www.bing.com',     'http://www.cnblogs.com/' ]   pool = ThreadPoolExecutor(5)   for url in url_list:     v = pool.submit(fetch_async,url)     #这里调用回调函数     v.add_done_callback(callback)   pool.shutdown()

四、通过进程池
进程池的方式访问，同样的也是取决于耗时最长的，但是相对于线程来说，进程需要耗费更多的资源，同时这里是访问url时IO操作，所以这里线程池比进程池更好

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import requests from concurrent.futures import ProcessPoolExecutor   def fetch_request(url):     result = requests.get(url)     print(result.text)   url_list = [     'http://www.baidu.com',     'http://www.bing.com',     'http://www.cnblogs.com/' ] pool = ProcessPoolExecutor(10)   for url in url_list:     #去进程池中获取一个线程，子进程程去执行fetch_request方法     pool.submit(fetch_request,url)   pool.shutdown(True)

五、进程池+回调函数
这种方式和线程+回调函数的效果是一样的，相对来说开进程比开线程浪费资源

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from concurrent.futures import ProcessPoolExecutor import requests     def fetch_async(url):     response = requests.get(url)       return response     def callback(future):     print(future.result().text)     url_list = [     'http://www.baidu.com',     'http://www.bing.com',     'http://www.cnblogs.com/' ]   pool = ProcessPoolExecutor(5)   for url in url_list:     v = pool.submit(fetch_async, url)     # 这里调用回调函数     v.add_done_callback(callback)   pool.shutdown()