以CSDN网站的登录为例，这里用Python的requests库与pytesser库写了一个登录函数。如果需要输入验证码，函数会首先下载验证码到本地，然后用pytesser识别验证码后登录，对于CSDN登录验证码，pytesser的识别率很高。
#coding:utf-8import sysimport timeimport urllibimport shutilimport pytesserimport requestsfrom lxml import etreeconfig = {'gid': 1}def parse(s, html, idx): result = {} tree = etree.HTML(html) try: result['lt'] = tree.xpath('//input[@name="lt"]/@value')[0] result['execution'] = tree.xpath('//input[@name="execution"]/@value')[0] result['path'] = tree.xpath('//form[@id="fm1"]/@action')[0] except IndexError, e: return None valimg = None valimgs = tree.xpath('//img[@id="yanzheng"]/@src') if len(valimgs) > 0: valimg = valimgs[0] validateCode = None if valimg: fname = 'img/' + str(idx) + '_' + str(config['gid']) + '.jpg' config['gid'] = config['gid'] + 1 ri = s.get("https://passport.csdn.net" + valimg) with open(fname, 'wb') as f: for chk in ri: f.write(chk) f.close() validateCode = pytesser.image_file_to_string(fname) validateCode = validateCode.strip() validateCode = validateCode.replace(' ', '') validateCode = validateCode.replace('/n', '') result['validateCode'] = validateCode return resultdef login(usr, pwd, idx): s = requests.Session() r = s.get('https://passport.csdn.net/account/login', headers={'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64; rv:41.0) Gecko/20100101 Firefox/41.0', 'Host': 'passport.csdn.net', }) while True: res = parse(s, r.text, idx) if res == None: return False url = 'https://passport.csdn.net' + res['path'] form = {'username': usr, 'password':pwd, '_eventId':'submit', 'execution':res['execution'], 'lt':res['lt'],} if res.has_key('validateCode'): form['validateCode'] = res['validateCode'] s.headers.update({ 'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64; rv:41.0) Gecko/20100101 Firefox/41.0', 'Accept-Language': 'zh-CN,zh;q=0.8,en-US;q=0.6,en;q=0.4', 'Content-Type': 'application/x-www-form-urlencoded', 'Host': 'passport.csdn.net', 'Origin': 'https://passport.csdn.net', 'Referer': 'https://passport.csdn.net/account/login', 'Upgrade-Insecure-Requests': 1, }) r = s.post(url, data=form) tree = etree.HTML(r.text) err_strs = tree.xpath('//span[@id="error-message"]/text()') if len(err_strs) == 0: return True err_str = err_strs[0] print err_str err = err_str.encode('utf8') validate_code_err = '验证码错误' usr_pass_err = '帐户名或登录密码不正确，请重新输入' try_later_err = '登录失败连续超过5次，请10分钟后再试' if err[:5] == validate_code_err[:5]: pass elif err[:5] == usr_pass_err[:5]: return False elif err[:5] == try_later_err[:5]: return False else: return Trueif __name__ == '__main__': main(sys.argv[1], sys.argv[2], 0) 
