首先导入模块，用help查看相关文档
>>> from urlparse import urljoin>>> help(urljoin)Help on function urljoin in module urlparse:urljoin(base, url, allow_fragments=True) ???Join a base URL and a possibly relative URL to form an absolute ???interpretation of the latter. ???
1 | 意思就是将基地址与一个相对地址形成一个绝对地址，然而讲的太过抽象 |
接下来，看几个例子，从例子中发现规律。
>>> urljoin("http://www.google.com/1/aaa.html","bbbb.html")‘http://www.google.com/1/bbbb.html‘>>> urljoin("http://www.google.com/1/aaa.html","2/bbbb.html")‘http://www.google.com/1/2/bbbb.html‘>>> urljoin("http://www.google.com/1/aaa.html","/2/bbbb.html")‘http://www.google.com/2/bbbb.html‘>>> urljoin("http://www.google.com/1/aaa.html","http://www.google.com/3/ccc.html")‘http://www.google.com/3/ccc.html‘>>> urljoin("http://www.google.com/1/aaa.html","http://www.google.com/ccc.html")‘http://www.google.com/ccc.html‘>>> urljoin("http://www.google.com/1/aaa.html","javascript:void(0)")‘javascript:void(0)‘规律不难发现，但是并不是万事大吉了，还需要处理特殊情况，如链接是其本身，链接中包含无效字符等
1 | url = urljoin("****","****")<br><br>### find()查找字符串函数，如果查到：返回查找到的第一个出现的位置。否则，返回-1<br>if url.find("‘")!=-1:<br> continue <br><br>### 只取井号前部分<br>url = url.split(‘#‘)[0]<br><br>### 这个isindexed()是我自己定义的函数，判断该链接不在保存链接的数据库中<br>if url[0:4]==‘http‘ and not self.isindexed(url):<br><br> ###newpages = set(),无序不重复元素集<br> newpages.add(url) |
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爬虫学习-urlparse之urljoin()
原文地址：https://www.cnblogs.com/php-linux/p/9680193.html