最近想练练爬虫，就写了这么一个东西。说起来，Python干这种事真是得心应手。因为我也是看了别人的文章学来的，所以就不讲解啦，只贴代码。

#!usr/bin/env python
# coding:utf-8

import requests
import os
import json
from lxml import etree


class ZhihuClient(object):
    """知乎爬虫，目前只能初步的登陆知乎"""

    def __init__(self):
        super(ZhihuClient, self).__init__()
        self.__session = requests.Session()
        self.__session.headers = {
            "User-Agent": "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36",
            "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
            "Accept-Encoding": "gzip, deflate",
            "Host": "www.zhihu.com",
            "Upgrade-Insecure-Requests": "1",
        }
        self.captchaFilepath = '/Users/lz/Desktop/cap.gif'
        self.isLogin = False

    def loadHome(self):
        """载入知乎首页"""
        self.__cookie = self.__loadCookie()
        if self.__cookie:
            print('拥有cookie，直接登录')
            self.__session.cookies.update(self.__cookie)
            home = self.__session.get('http://www.zhihu.com').text
            with open('home.html', 'w') as f:
                f.write(home)
        else:
            print('缺少cookie，请登录')
            username = input('请输入你的用户名:')
            password = input('请输入你的密码')
            self.login(username, password)
            home = self.__session.get('http://www.zhihu.com').text
            with open('home.html', 'w') as f:
                f.write(home)

    def login(self, username, password):
        """登陆知乎"""
        self.setusername(username)
        self.__password = password
        html = self.__session.get('http://www.zhihu.com').text
        html = etree.HTML(html.lower())
        print(type(html))
        result = html.xpath('//input[@name="_xsrf"]')
        self.__xsrf = result[0].attrib['value']
        self.getgif()
        data = {
            '_xsrf': self.__xsrf,
            'password': self.__password,
            'remember_me': 'true',
            self.__usernametype: self.__username,
            'captcha': self.__captcha
        }
        res = self.__session.post(
            'http://www.zhihu.com/login/' + self.__usernametype, data=data)
        print('=' * 50)
        if res.json()['r'] == 0:
            print('登陆成功')
            self.__saveCookie()
        else:
            print('登陆失败')
            print('错误信息 ----- >', res.json()['msg'])

    def getgif(self):
        """获取验证码图片"""
        captcha = self.__session.get(
            'http://www.zhihu.com/captcha.gif').content
        with open(self.captchaFilepath, 'wb') as output:
            output.write(captcha)
        print('=' * 50)
        self.__captcha = input('请输入验证码:')
        os.remove(self.captchaFilepath)

    def setusername(self, username):
        """检测登陆类型"""
        self.__username = username
        if username.isdigit():
            self.__usernametype = 'phone_num'
        else:
            self.__usernametype = 'email'

    def loadUrl(self, url):
        """下载传入的url指向页面中所有答案的图片"""
        htmlS = self.__session.get(url).text
        html = etree.HTML(htmlS.lower())
        result = html.xpath('//span[@class="zm-editable-content"]')
        name = result[0].text
        path = name + '/'
        os.mkdir(name)
        if os.path.exists(name):
            with open(path + name + '.html', 'w') as f:
                f.write(htmlS)
            print('目标网页获取成功')
            result = html.xpath(
                '//img[@class="origin_image zh-lightbox-thumb"]')
            imgs = []
            for ele in result:
                imgs.append(ele.attrib["src"])
            self.downloadImg(imgs, path)

    def downloadImg(self, imgs, path):
        """通过传入的imgs链接，下载图片"""
        length = len(imgs)
        for i in range(0, length):
            url = imgs[i]
            print(url)
            img = requests.get(url).content
            with open(path + '%d.png' % i, 'wb') as f:
                f.write(img)

    def __saveCookie(self):
        """储存cookie"""
        with open('zhihucookie', 'w') as f:
            json.dump(self.__session.cookies.get_dict(), f)
        print('=' * 50)
        print('已经生成cookiew文件')

    def __loadCookie(self):
        """加载cookie"""
        if os.path.exists('zhihucookie'):
            print('=' * 50)
            with open('zhihucookie', 'r') as f:
                cookie = json.load(f)
            self.isLogin = True
            return cookie
        return None

if __name__ == '__main__':
    client = ZhihuClient()
    if not client.isLogin:
        print('我要登录')
        client.loadHome()
    url = input('请输入网址:')
    client.loadUrl(url)