作為一個Python菜鳥，之前一直懵懂于urllib和urllib2，以為2是1的升級版。今天看到老外寫的一篇《Python: difference between urllib and urllib2》才明白其中的區別

You might be intrigued by the existence of two separate URL modules in Python -urllib and urllib2. Even more intriguing: they are not alternatives for each other. So what is the difference between urllib and urllib2, and do we need them both?

你可能對于Python中兩個獨立存在的-urllib2和-urllib2感到好奇。更有趣的是：它們并不是可以相互代替的。那么這兩個模塊間的區別是什么，并且這兩個我們都需要嗎？

urllib and  urllib2are both Python modules that do URL request related stuff but offer different functionalities. Their two most significant differences are listed below:

urllib 和urllib2都是接受URL請求的相關模塊，但是提供了不同的功能。兩個最顯著的不同如下：

•urllib2 can accept a Request object to set the headers for a URL request,urllib accepts only a URL. That means, you cannot masquerade your User Agent string etc.

urllib2可以接受一個Request類的實例來設置URL請求的headers，urllib僅可以接受URL。這意味著，你不可以偽裝你的User Agent字符串等。

•urllib provides the urlencode method which is used for the generation of GET query strings, urllib2 doesn't have such a function. This is one of the reasons why urllib is often used along with urllib2.

urllib提供urlencode方法用來GET查詢字符串的產生，而urllib2沒有。這是為何urllib常和urllib2一起使用的原因。 

 For other differences between urllib and urllib2 refer to their documentations, the links are given in the References section.
Tip: if you are planning to do HTTP stuff only, check out httplib2, it is much better than httplib or urllib or urllib2.

提示：如果你僅做HTTP相關的，看一下httplib2，比其他幾個模塊好用。

相關資料

這里還有個類似的問答：urllib urllib2 what is the difference ?

stackoverflow上也有：Should I use urllib or urllib2?

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