Python Mechanize : HTTP Error 428 Precondition Failed

Question

我正在尝试使用 python mechanize 模块在网站上自动化一个过程。

使用以下代码，我将刷新站点，直到找到我想要关注的链接:

            for link in br.links():            
               valuable = filter(lambda tpl: tpl[0]=='href', link.attrs)
               if len(valuable) == 0:
                   continue
               if 'book.php' in valuable[0][1]:
                   print link
                   req = br.follow_link(link)
                   file_handler = open("level2.html", "w")
                   file_handler.write(br.response().read())
                   file_handler.close()
                   not_done = False
                   break

一旦我找到包含“book.php”的链接，应用程序就会崩溃并出现以下错误:

File "/home/max/Dokumente/dev/main.py", line 43, in run req = br.follow_link(link)

File "build/bdist.linux-x86_64/egg/mechanize/_mechanize.py", line 569, in follow_link

File "build/bdist.linux-x86_64/egg/mechanize/_mechanize.py", line 203, in open

File "build/bdist.linux-x86_64/egg/mechanize/_mechanize.py", line 255, in _mech_open

mechanize._response.httperror_seek_wrapper: HTTP Error 428: Precondition failed

这意味着什么？我真的想不通。我该如何解决这个错误？

Answer 1

如解释 here :

The origin server requires the request to be conditional. Its typical use is to avoid the "lost update" problem, where a client GETs a resource's state, modifies it, and PUTs it back to the server, when meanwhile a third party has modified the state on the server, leading to a conflict.

这可能意味着已处理链接中的 GET 参数突然过时了。