# coding=utf-8 
import requests 
from bs4 import BeautifulSoup

headers = { 
'user-agent': 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36', 
'origin': 'https://www.v2ex.com', 
'referer': 'https://www.v2ex.com/signin', 
'host': 'www.v2ex.com', 
} 
s = requests.Session() 
r = s.get('https://www.v2ex.com/signin', headers=headers) 
soup = BeautifulSoup(r.content, "html.parser")

#获取登录数据
once = soup.find('input', {'name': 'once'})['value']
name = soup.find('input', {'type': 'text', 'class': 'sl'})['name']
password = soup.find('input', {'type': 'password', 'class': 'sl'})['name']
login_data = {
name : 'xxx',
password : 'xxx',
'once' : once,
'next' : '/'
}

#登录 
s.post('https://www.v2ex.com/signin', login_data, headers=headers)