利用python的urllib2库写爬虫自动登录12306

HTTP是无状态的协议，一个网站标记用户的标识用的是cookie，即使是服务器里的session，也会在客户端种植一个cookie来指定这个session。因此，要想模拟登录一个网站，就是要跟踪它的cookie(包括接收和发送)，除了跟踪cookie，有的还需要修改ua(User-Agent)，伪装成正常的浏览器。而python的urllib2库在与服务器交互时正好可以自动保存和发送cookie，抓取网页和模拟登录相当的便利。

要模拟登录12306，需要输入验证码，在登录表单提交时，页面还会去服务器获取一次随机码，然后才会将随机码和用户名、密码、验证码一并提交，这个过程中，需要接收和发送服务器设置的cookie(即同步cookie)才能登录成功。

下面是代码的实现，非常简单，登录成功后就能继续写模拟查票订票的功能了。

# -*- coding: gb2312 -*-
# env: python2.7

import urllib2
from urllib import urlencode
from cookielib import LWPCookieJar
from time import strftime, sleep
from getpass import getpass
from re import compile

class curl:

    def __init__(self):
        self.logindata = {}
        self.username = ''
        self.password = ''
        self.randcode = ''
        self.ifneedrefreshrandcode = True   #重复登录时是否需要重新输入验证码

        #在http交互中即时更新cookie
        self.cookiejar = LWPCookieJar()
        cookiesupport = urllib2.HTTPCookieProcessor(self.cookiejar)
        opener = urllib2.build_opener(cookiesupport, urllib2.HTTPHandler)
        urllib2.install_opener(opener)

    #生成验证码图片文件
    def getrandcode(self):
        try:
            response = urllib2.urlopen('http://dynamic.12306.cn/otsweb/passCodeAction.do?rand=sjrand')
            imgdata = response.read()
            f = file('./验证码.jpg', 'wb')
            f.write(imgdata)
            f.close()
        except:
            pass

    #获取随机码
    def getloginrand(self):
        try:
            response = urllib2.urlopen('http://dynamic.12306.cn/otsweb/loginAction.do?method=loginAysnSuggest')
            re = compile('loginRand":"(\d+)"')
            match = re.search(response.read())
            return match.group(1)
        except:
            pass

    #登录动作
    def login(self, loginrand = ''):
        self.logindata['loginRand'] = loginrand                 #随机码
        self.logindata['refundLogin'] = 'N'
        self.logindata['refundFlag'] = 'Y'
        self.logindata['loginUser.user_name'] = self.username   #用户名
        self.logindata['nameErrorFocus'] = ''
        self.logindata['user.password'] = self.password         #用户密码
        self.logindata['passwordErrorFocus'] = ''
        self.logindata['randCode'] = self.randcode              #验证码
        self.logindata['randErrorFocus'] = ''

        try:
            req = urllib2.Request('http://dynamic.12306.cn/otsweb/loginAction.do?method=login', urlencode(self.logindata))
            data = urllib2.urlopen(req)
            text = data.read().decode('utf-8').encode('gb2312') #将utf-8解码再编码为gb2312
            return text
        except:
            pass

    #将cookie打印出来，登录成功后可以将此cookie代码弄到浏览器的12306页面里，再刷新页面就直接登录成功了
    def getcookie(self):
        text = '/' + '*' * 20 + ' 会话生成日期：' + strftime('%Y-%m-%d %H:%M:%S') + ' ' + '*' * 20
        cookiestring = '/\r\n\r\njavascript:'
        for c in self.cookiejar:
            cookiestring += " document.cookie = '" + c.name + '=' + c.value + '; path=' + c.path + "';"
        cookiestring += ' void(0);'
        f = file('./会话.txt', 'w')
        f.write(text + cookiestring)
        f.close()

def main():

    while ch.username == '':
        ch.username = raw_input('输入12306登录的用户名：\n')
    while len(ch.password) < 6:
        print '\r密码：',
        ch.password = getpass('\n')
    print '\r'

    if ch.ifneedrefreshrandcode:
        print '正在生成验证码...'
        ch.getrandcode()
        ch.randcode = ''
        while len(ch.randcode) != 4:
            ch.randcode = raw_input('验证码已生成，请查看文件夹下的"验证码.jpg"并输入验证码：\n')

    print '正在生成随机码...'
    loginrand = ch.getloginrand()
    print '随机码：' + loginrand

    print '登陆中...'
    text = ch.login(loginrand)

    reg = compile('var\sisLogin\s?=\strue')
    match = reg.search(text)
    msg = None
    if match:
        reg = compile("var\su_name\s=\s'(.+)'")
        match = reg.search(text)
        if match:
            msg = match.group(1)
            print msg + '，登陆成功'
            ch.getcookie()
            print '会话文件已生成，请查看文件夹下的"会话.txt"'
            raw_input('Press <Enter>')
            return True
    else:
        reg = compile('var\smessage\s=\s"(.+)"')
        match = reg.search(text)
        if match:
            msg = match.group(1)
            print msg
            ch.ifneedrefreshrandcode = False
            if '密码输入错误' in msg or '登录名不存在' in msg or '已经被锁定' in msg:
                ch.username = ''
                ch.password = ''
            else:
                print '5秒后尝试重新登录...'
                sleep(5)
            main()
            return False
        elif 'images/er/tools_ico2.gif' in text:
            print '验证码错误'
            ch.ifneedrefreshrandcode = True
            main()
            return False

    if '/otsweb/images/warn.gif' in text:
        print '系统打烊中...'
        raw_input('Press <Enter>')
    else:
        print '登录失败，5秒后尝试重新登录...'
        sleep(5)
        main()

    return True

if __name__ == '__main__':
    ch = curl()
    main()

#end