goagent用到的模块简介

1. base64

base64模块是用来作base64编码解码的。这种编码方式在电子邮件中是很常见的。
它可以把不能作为文本显示的二进制数据编码为可显示的文本信息。编码后的文本大小会增大1/3。

    闲话不说了，base64模块真正用的上的方法只有8个，分别是encode, decode, encodestring, decodestring, b64encode,b64decode, urlsafe_b64decode,urlsafe_b64encode。他们8个可以两两分为4组，encode,decode一组，专门用来编码和 解码文件的,也可以对StringIO里的数据做编解码；encodestring,decodestring一组，专门用来编码和解码字符串； b64encode和b64decode一组，用来编码和解码字符串，并且有一个替换符号字符的功能。这个功能是这样的：因为base64编码后的字符除 了英文字母和数字外还有三个字符 + / =, 其中=只是为了补全编码后的字符数为4的整数，而+和/在一些情况下需要被替换的，b64encode和b64decode正是提供了这样的功能。至于什 么情况下+和/需要被替换，最常见的就是对url进行base64编码的时候。urlsafe_b64encode和urlsafe_b64decode 一组，这个就是用来专门对url进行base64编解码的，实际上也是调用的前一组函数。

def proxy_basic_auth_header(self):        return 'Proxy-Authorization: Basic %s' + base64.b64encode('%s:%s'%(self.PROXY_USERNAME, self.PROXY_PASSWROD))

2. urllib2

在网上找了一下关于urllib2模块的介绍，都比较简单，下面是从python文档中找的，贴了一部分。

一句话概括的话：urllib2是一个可扩展的库，可根据不同的协议打开URLs。

>>> help (urllib2)Help on module urllib2:NAME    urllib2 - An extensible library for opening URLs using a variety of protocolsFILE    c:\python27\lib\urllib2.pyDESCRIPTION    The simplest way to use this module is to call the urlopen function,    which accepts a string containing a URL or a Request object (described    below).  It opens the URL and returns the results as file-like    object; the returned object has some extra methods described below.        The OpenerDirector manages a collection of Handler objects that do    all the actual work.  Each Handler implements a particular protocol or    option.  The OpenerDirector is a composite object that invokes the    Handlers needed to open the requested URL.  For example, the    HTTPHandler performs HTTP GET and POST requests and deals with    non-error returns.  The HTTPRedirectHandler automatically deals with    HTTP 301, 302, 303 and 307 redirect errors, and the HTTPDigestAuthHandler    deals with digest authentication.        urlopen(url, data=None) -- Basic usage is the same as original    urllib.  pass the url and optionally data to post to an HTTP URL, and    get a file-like object back.  One difference is that you can also pass    a Request instance instead of URL.  Raises a URLError (subclass of    IOError); for HTTP errors, raises an HTTPError, which can also be    treated as a valid response.        build_opener -- Function that creates a new OpenerDirector instance.    Will install the default handlers.  Accepts one or more Handlers as    arguments, either instances or Handler classes that it will    instantiate.  If one of the argument is a subclass of the default    handler, the argument will be installed instead of the default.        install_opener -- Installs a new opener as the default opener.

def install_opener(self):        if self.PROXY_ENABLE:            proxy = '%s:%s@%s:%d'%(self.PROXY_USERNAME, self.PROXY_PASSWROD, self.PROXY_HOST, self.PROXY_PORT)            handlers = [urllib2.ProxyHandler({'http':proxy,'https':proxy})]            if self.PROXY_NTLM:                if ntlm is None:                    logging.critical('You need install python-ntlm to support windows domain proxy! "%s:%s"', self.PROXY_HOST, self.PROXY_PORT)                    sys.exit(-1)                passman = urllib2.HTTPPasswordMgrWithDefaultRealm()                passman.add_password(None, '%s:%s' % (self.PROXY_HOST, self.PROXY_PORT), self.PROXY_USERNAME, self.PROXY_PASSWROD)                auth_NTLM = ntlm.HTTPNtlmAuthHandler.HTTPNtlmAuthHandler(passman)                handlers.append(auth_NTLM)        else:            handlers = [urllib2.ProxyHandler({})]        opener = urllib2.build_opener(*handlers)        opener.addheaders = []        urllib2.install_opener(opener)