python 使用 mechanize 模拟浏览器访问网页

知道如何快速在命令行或者python脚本中实例化一个浏览器通常是非常有用的。

每次我需要做任何关于web的自动任务时，我都使用这段python代码去模拟一个浏览器。

import mechanize
import cookielib
# Browser
br = mechanize.Browser()
# Cookie Jar
cj = cookielib.LWPCookieJar()
br.set_cookiejar(cj)
# Browser options
br.set_handle_equiv(True)
br.set_handle_gzip(True)
br.set_handle_redirect(True)
br.set_handle_referer(True)
br.set_handle_robots(False)
# Follows refresh 0 but not hangs on refresh > 0
br.set_handle_refresh(mechanize._http.HTTPRefreshProcessor(), max_time=1)
# Want debugging messages?
#br.set_debug_http(True)
#br.set_debug_redirects(True)
#br.set_debug_responses(True)
# User-Agent (this is cheating, ok?)
br.addheaders = [('User-agent', 'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.1) Gecko/2008071615 Fedora/3.0.1-1.fc9 Firefox/3.0.1')]

现在你得到了一个浏览器的示例，br对象。使用这个对象，便可以打开一个页面，使用类似如下的代码:

# Open some site, let's pick a random one, the first that pops in mind:
r = br.open('http://google.com')
html = r.read()
# Show the source
print html
# or
print br.response().read()
# Show the html title
print br.title()
# Show the response headers
print r.info()
# or
print br.response().info()
# Show the available forms
for f in br.forms():
        print f
# Select the first (index zero) form
br.select_form(nr=0)
# Let's search
br.form['q']='weekend codes'
br.submit()
print br.response().read()
# Looking at some results in link format
for l in br.links(url_regex='stockrt'):
        print l

如果你访问的网站需要验证(http basic auth),那么:

# If the protected site didn't receive the authentication data you would
# end up with a 410 error in your face
br.add_password('http://safe-site.domain', 'username', 'password')
br.open('http://safe-site.domain')

由于之前使用了Cookie Jar，你不需要管理网站的登录session。也就是不需要管理需要POST一个用户名和密码的情况。
通常这种情况，网站会请求你的浏览器去存储一个session cookie除非你重复登陆，
而导致你的cookie中含有这个字段。所有这些事情，存储和重发这个session cookie已经被Cookie Jar搞定了，爽吧。
同时，你可以管理你的浏览器历史:

# Testing presence of link (if the link is not found you would have to
# handle a LinkNotFoundError exception)
br.find_link(text='Weekend codes')
# Actually clicking the link
req = br.click_link(text='Weekend codes')
br.open(req)
print br.response().read()
print br.geturl()
# Back
br.back()
print br.response().read()
print br.geturl()

下载一个文件:

# Download
f = br.retrieve('http://www.google.com.br/intl/pt-BR_br/images/logo.gif')[0]
print f
fh = open(f)

为http设置代理

# Proxy and user/password
br.set_proxies({"http": "joe:[email protected]:3128"})
# Proxy
br.set_proxies({"http": "myproxy.example.com:3128"})
# Proxy password
br.add_proxy_password("joe", "password")

但是，如果你只想要打开网页，而不需要之前所有神奇的功能，那你可以:

# Simple open?
import urllib2
print urllib2.urlopen('http://stockrt.github.com').read()
# With password?
import urllib
opener = urllib.FancyURLopener()
print opener.open('http://user:[email protected]').read()