- 提出问题：如何简单抓取一个网页的源码
- 解决方法：利用urllib库，抓取一个网页的源代码
------------------------------------------------------------------------------------
- 代码示例
#python3.4
import urllib.request
response = urllib.request.urlopen("http://zzk.cnblogs.com/b")
print(response.read())
- 运行结果
b'
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<title>xe6x89xbexe6x89xbexe7x9cx8b - xe5x8dx9axe5xaexa2xe5x9bxad</title>
<link rel="shortcut icon" href="/Content/Images/favicon.ico" type="image/x-icon"/>
<meta content="xe6x8ax80xe6x9cxafxe6x90x9cxe7xb4xa2,ITxe6x90x9cxe7xb4xa2,xe7xa8x8bxe5xbax8fxe6x90x9cxe7xb4xa2,xe4xbbxa3xe7xa0x81xe6x90x9cxe7xb4xa2,xe7xa8x8bxe5xbax8fxe5x91x98xe6x90x9cxe7xb4xa2xe5xbcx95xe6x93x8e" name="keywords" />
<meta content="xe9x9dxa2xe5x90x91xe7xa8x8bxe5xbax8fxe5x91x98xe7x9ax84xe4xb8x93xe4xb8x9axe6x90x9cxe7xb4xa2xe5xbcx95xe6x93x8exe3x80x82xe9x81x87xe5x88xb0xe6x8ax80xe6x9cxafxe9x97xaexe9xa2x98xe6x80x8exe4xb9x88xe5x8ax9exefxbcx8cxe5x88xb0xe5x8dx9axe5xaexa2xe5x9bxadxe6x89xbexe6x89xbexe7x9cx8b..." name="description" />
<link type="text/css" href="/Content/Style.css" rel="stylesheet" />
<script src="http://common.cnblogs.com/script/jquery.js" type="text/javascript"></script>
<script src="/Scripts/Common.js" type="text/javascript"></script>
<script src="/Scripts/Home.js" type="text/javascript"></script>
</head>
<body>
<div class="top">
<div class="top_tabs">
<a href="http://www.cnblogs.com">xc2xab xe5x8dx9axe5xaexa2xe5x9bxadxe9xa6x96xe9xa1xb5 </a>
</div>
<div id="span_userinfo" class="top_links">
</div>
</div>
<div style="clear: both">
</div>
<center>
<div id="main">
<div class="logo_index">
<a href="http://zzk.cnblogs.com">
<img alt="xe6x89xbexe6x89xbexe7x9cx8blogo" src="/images/logo.gif" /></a>
</div>
<div class="index_sozone">
<div class="index_tab">
<a href="/n" onclick="return channelSwitch('n');">xe6x96xb0xe9x97xbb</a>
<a class="tab_selected" href="/b" onclick="return channelSwitch('b');">xe5x8dx9axe5xaexa2</a> <a href="/k" onclick="return channelSwitch('k');">xe7x9fxa5xe8xafx86xe5xbax93</a>
<a href="/q" onclick="return channelSwitch('q');">xe5x8dx9axe9x97xae</a>
</div>
<div class="search_block">
<div class="index_btn">
<input type="button" class="btn_so_index" onclick="Search();" value=" xe6x89xbexe4xb8x80xe4xb8x8b " />
<span class="help_link"><a target="_blank" href="/help">xe5xb8xaexe5x8axa9</a></span>
</div>
<input type="text" onkeydown="searchEnter(event);" class="input_index" name="w" id="w" />
</div>
</div>
</div>
<div class="footer">
©2004-2016 <a href="http://www.cnblogs.com">xe5x8dx9axe5xaexa2xe5x9bxad</a>
</div>
</center>
</body>
</html>
'
- 附上python2.7的实现代码：
#python2.7
import urllib2
response = urllib2.urlopen("http://zzk.cnblogs.com/b")
print response.read()
- 可见，python3.4和python2.7的代码存在差异性。
----------@_@？ 问题出现！----------------------------------------------------------------------
- 发现问题：查看上面的运行结果，会发现中文并没有正常显示。
- 解决问题：处理中文编码问题
--------------------------------------------------------------------------------------------------
- 处理源码中的中文问题！！！
- 修改代码，如下：
#python3.4
import urllib.request
response = urllib.request.urlopen("http://zzk.cnblogs.com/b")
print(response.read().decode('UTF-8'))
- 运行，结果显示：
C:Python34python.exe E:/pythone_workspace/mydemo/spider/demo.py
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<title>找找看 - 博客园</title>
<link rel="shortcut icon" href="/Content/Images/favicon.ico" type="image/x-icon"/>
<meta content="技术搜索,IT搜索,程序搜索,代码搜索,程序员搜索引擎" name="keywords" />
<meta content="面向程序员的专业搜索引擎。遇到技术问题怎么办，到博客园找找看..." name="description" />
<link type="text/css" href="/Content/Style.css" rel="stylesheet" />
<script src="http://common.cnblogs.com/script/jquery.js" type="text/javascript"></script>
<script src="/Scripts/Common.js" type="text/javascript"></script>
<script src="/Scripts/Home.js" type="text/javascript"></script>
</head>
<body>
<div class="top">
<div class="top_tabs">
<a href="http://www.cnblogs.com">« 博客园首页 </a>
</div>
<div id="span_userinfo" class="top_links">
</div>
</div>
<div style="clear: both">
</div>
<center>
<div id="main">
<div class="logo_index">
<a href="http://zzk.cnblogs.com">
<img alt="找找看logo" src="/images/logo.gif" /></a>
</div>
<div class="index_sozone">
<div class="index_tab">
<a href="/n" onclick="return channelSwitch('n');">新闻</a>
<a class="tab_selected" href="/b" onclick="return channelSwitch('b');">博客</a> <a href="/k" onclick="return channelSwitch('k');">知识库</a>
<a href="/q" onclick="return channelSwitch('q');">博问</a>
</div>
<div class="search_block">
<div class="index_btn">
<input type="button" class="btn_so_index" onclick="Search();" value=" 找一下 " />
<span class="help_link"><a target="_blank" href="/help">帮助</a></span>
</div>
<input type="text" onkeydown="searchEnter(event);" class="input_index" name="w" id="w" />
</div>
</div>
</div>
<div class="footer">
©2004-2016 <a href="http://www.cnblogs.com">博客园</a>
</div>
</center>
</body>
</html>
Process finished with exit code 0
- 结果显示：处理完编码后，网页源码中中文可以正常显示了
-----------@_@! 探讨一个新的中文编码问题 ----------------------------------------------------------
问题：“如果url中出现中文，那么应该如果解决呢？”
例如：url = "http://zzk.cnblogs.com/s?w=python爬虫&t=b"
-----------------------------------------------------------------------------------------------------
- 接下来，我们来解决url中出现中文的问题！！！
（1）测试1：保留原来的格式，直接访问，不做任何处理
- 代码示例：
#python3.4
import urllib.request
url="http://zzk.cnblogs.com/s?w=python爬虫&t=b"
resp = urllib.request.urlopen(url)
print(resp.read().decode('UTF-8'))
- 运行结果：
C:Python34python.exe E:/pythone_workspace/mydemo/spider/demo.py
Traceback (most recent call last):
File "E:/pythone_workspace/mydemo/spider/demo.py", line 9, in <module>
response = urllib.request.urlopen(url)
File "C:Python34liburllib
equest.py", line 161, in urlopen
return opener.open(url, data, timeout)
File "C:Python34liburllib
equest.py", line 463, in open
response = self._open(req, data)
File "C:Python34liburllib
equest.py", line 481, in _open
'_open', req)
File "C:Python34liburllib
equest.py", line 441, in _call_chain
result = func(*args)
File "C:Python34liburllib
equest.py", line 1210, in http_open
return self.do_open(http.client.HTTPConnection, req)
File "C:Python34liburllib
equest.py", line 1182, in do_open
h.request(req.get_method(), req.selector, req.data, headers)
File "C:Python34libhttpclient.py", line 1088, in request
self._send_request(method, url, body, headers)
File "C:Python34libhttpclient.py", line 1116, in _send_request
self.putrequest(method, url, **skips)
File "C:Python34libhttpclient.py", line 973, in putrequest
self._output(request.encode('ascii'))
UnicodeEncodeError: 'ascii' codec can't encode characters in position 15-16: ordinal not in range(128)
Process finished with exit code 1
果然不行！！！
（2）测试2：中文单独处理
- 代码示例：
import urllib.request
import urllib.parse
url = "http://zzk.cnblogs.com/s?w=python"+ urllib.parse.quote("爬虫")+"&t=b"
resp = urllib.request.urlopen(url)
print(resp.read().decode('utf-8'))
- 运行结果：
运行结果- 结果显示：对url中的中文进行单独处理，url对应内容可以正常抓取了
------@_@! 又有一个新的问题-----------------------------------------------------------
- 问题：如果把url的中英文一起进行处理呢？还能成功抓取吗？
----------------------------------------------------------------------------------------
（3）于是，测试3出现了！测试3：url中，中英文一起进行处理
- 代码示例：
#python3.4
import urllib.request
import urllib.parse
url = urllib.parse.quote("http://zzk.cnblogs.com/s?w=python爬虫&t=b")
resp = urllib.request.urlopen(url)
print(resp.read().decode('utf-8'))
- 运行结果：
C:Python34python.exe E:/pythone_workspace/mydemo/spider/demo.py
Traceback (most recent call last):
File "E:/pythone_workspace/mydemo/spider/demo.py", line 21, in <module>
resp = urllib.request.urlopen(url)
File "C:Python34liburllib
equest.py", line 161, in urlopen
return opener.open(url, data, timeout)
File "C:Python34liburllib
equest.py", line 448, in open
req = Request(fullurl, data)
File "C:Python34liburllib
equest.py", line 266, in __init__
self.full_url = url
File "C:Python34liburllib
equest.py", line 292, in full_url
self._parse()
File "C:Python34liburllib
equest.py", line 321, in _parse
raise ValueError("unknown url type: %r" % self.full_url)
ValueError: unknown url type: 'http%3A//zzk.cnblogs.com/s%3Fw%3Dpython%E7%88%AC%E8%99%AB%26t%3Db'
Process finished with exit code 1
- 结果显示：ValueError！无法成功抓取网页！
- 结合测试1、2、3，可得到下面结果：
（1）在python3.4中，如果url中包含中文，可以用 urllib.parse.quote("爬虫") 进行处理。
（2）url中的中文需要单独处理，不能中英文一起处理。
- Tips：如果想了解一个函数的参数传值
#python3.4 import urllib.request
help(urllib.request.urlopen)
- 运行上面代码，控制台输出
C:Python34python.exe E:/pythone_workspace/mydemo/spider/demo.py Help on function urlopen in module urllib.request: urlopen(url, data=None, timeout=<object object at 0x00A50490>, *, cafile=None, capath=None, cadefault=False, context=None) Process finished with exit code 0