知乎模拟登录，支持验证码和保存 Cookies

 import requests
 import time
 import re
 import base64
 import hmac
 import hashlib
 import json
 import matplotlib.pyplot as plt
 from http import cookiejar
 from PIL import Image

 HEADERS = {
     'Connection': 'keep-alive',
     'Host': 'www.zhihu.com',
     'Referer': 'https://www.zhihu.com/',
     'User-Agent': 'Mozilla/5.0 (Linux; Android 6.0; Nexus 5 Build/MRA58N) AppleWebKit/537.36 '
                   '(KHTML, like Gecko) Chrome/56.0.2924.87 Mobile Safari/537.36'
     }
 LOGIN_URL = 'https://www.zhihu.com/signup'
 LOGIN_API = 'https://www.zhihu.com/api/v3/oauth/sign_in'
 FORM_DATA = {
     'client_id': 'c3cef7c66a1843f8b3a9e6a1e3160e20',
     'grant_type': 'password',
     'source': 'com.zhihu.web',
     'username': '',
     'password': '',
     # 改为'cn'是倒立汉字验证码
     'lang': 'en',
     'ref_source': 'homepage'
 }

 class ZhihuAccount(object):

     def __init__(self):
         self.login_url = LOGIN_URL
         self.login_api = LOGIN_API
         self.login_data = FORM_DATA.copy()
         self.session = requests.session()
         self.session.headers = HEADERS.copy()
         self.session.cookies = cookiejar.LWPCookieJar(filename='./cookies.txt')

     def login(self, username=None, password=None, load_cookies=True):
         """
         模拟登录知乎
         :param username: 登录手机号
         :param password: 登录密码
         :param load_cookies: 是否读取上次保存的 Cookies
         :return: bool
         """
         if load_cookies and self.load_cookies():
             if self.check_login():
                 return True

         headers = self.session.headers.copy()
         headers.update({
             'authorization': 'oauth c3cef7c66a1843f8b3a9e6a1e3160e20',
             'X-Xsrftoken': self._get_token()
         })
         username, password = self._check_user_pass(username, password)
         self.login_data.update({
             'username': username,
             'password': password
         })
         timestamp = str(int(time.time()*1000))
         self.login_data.update({
             'captcha': self._get_captcha(self.login_data['lang'], headers),
             'timestamp': timestamp,
             'signature': self._get_signature(timestamp)
         })

         resp = self.session.post(self.login_api, data=self.login_data, headers=headers)
         if 'error' in resp.text:
             print(json.loads(resp.text)['error']['message'])
         elif self.check_login():
             return True
         print('登录失败')
         return False

     def load_cookies(self):
         """
         读取 Cookies 文件加载到 Session
         :return: bool
         """
         try:
             self.session.cookies.load(ignore_discard=True)
             return True
         except FileNotFoundError:
             return False

     def check_login(self):
         """
         检查登录状态，访问登录页面出现跳转则是已登录，
         如登录成功保存当前 Cookies
         :return: bool
         """
         resp = self.session.get(self.login_url, allow_redirects=False)
         if resp.status_code == 302:
             self.session.cookies.save()
             print('登录成功')
             return True
         return False

     def _get_token(self):
         """
         从登录页面获取 token
         :return:
         """

         resp = requests.get("https://www.zhihu.com")
         cookies = resp.cookies
         token = cookies.items()[0][1]
         return token

     def _get_captcha(self, lang, headers):
         """
         请求验证码的 API 接口，无论是否需要验证码都需要请求一次
         如果需要验证码会返回图片的 base64 编码
         根据 lang 参数匹配验证码，需要人工输入
         :param lang: 返回验证码的语言(en/cn)
         :param headers: 带授权信息的请求头部
         :return: 验证码的 POST 参数
         """
         if lang == 'cn':
             api = 'https://www.zhihu.com/api/v3/oauth/captcha?lang=cn'
         else:
             api = 'https://www.zhihu.com/api/v3/oauth/captcha?lang=en'
         resp = self.session.get(api, headers=headers)
         show_captcha = re.search(r'true', resp.text)

         if show_captcha:
             put_resp = self.session.put(api, headers=headers)
             json_data = json.loads(put_resp.text)
             img_base64 = json_data['img_base64'].replace(r'\n', '')
             with open('./captcha.jpg', 'wb') as f:
                 f.write(base64.b64decode(img_base64))
             img = Image.open('./captcha.jpg')
             if lang == 'cn':
                 plt.imshow(img)
                 print('点击所有倒立的汉字，按回车提交')
                 points = plt.ginput(7)
                 capt = json.dumps({'img_size': [200, 44],
                                    'input_points': [[i[0]/2, i[1]/2] for i in points]})
             else:
                 img.show()
                 capt = input('请输入图片里的验证码：')
             # 这里必须先把参数 POST 验证码接口
             self.session.post(api, data={'input_text': capt}, headers=headers)
             return capt
         return ''

     def _get_signature(self, timestamp):
         """
         通过 Hmac 算法计算返回签名
         实际是几个固定字符串加时间戳
         :param timestamp: 时间戳
         :return: 签名
         """
         ha = hmac.new(b'd1b964811afb40118a12068ff74a12f4', digestmod=hashlib.sha1)
         grant_type = self.login_data['grant_type']
         client_id = self.login_data['client_id']
         source = self.login_data['source']
         ha.update(bytes((grant_type + client_id + source + timestamp), 'utf-8'))
         return ha.hexdigest()

     def _check_user_pass(self, username, password):
         """
         检查用户名和密码是否已输入，若无则手动输入
         """
         if username is None:
             username = self.login_data.get('username')
             if not username:
                 username = input('请输入手机号：')
         if len(username) == 11 and username.isdigit() and '+86' not in username:
             username = '+86' + username

         if password is None:
             password = self.login_data.get('password')
             if not password:
                 password = input('请输入密码：')
         return username, password

 if __name__ == '__main__':
     account = ZhihuAccount()
     account.login(username=None, password=None, load_cookies=True)

GitHub：https://github.com/liyunchen/Zhihu-Login/blob/master/zhihu_login.py