import scrapy
class LoginSpider(scrapy.Spider):
  name = 'login'
  allowed_domains = ['xxx.com']
  start_urls = ['https://www.xxx.com/xx/']
  cookies = ""
  def start_requests(self):
    for url in self.start_urls:
      yield scrapy.Request(url, cookies=self.cookies, callback=self.parse)
  def parse(self, response):
    with open("01login.html", "wb") as f:
      f.write(response.body)

import scrapy
class LoginSpider(scrapy.Spider):
  name='login_code'
  allowed_domains = ['xxx.com']
  #1. 登录页面
  start_urls = ['https://www.xxx.com/login/']
  def parse(self, response):
    #2. 代码登录
    login_url='https://www.xxx.com/login'
    formdata={
      "username":"xxx",
      "pwd":"xxx",
      "formhash":response.xpath("//input[@id='formhash']/@value").extract_first(),
      "backurl":response.xpath("//input[@id='backurl']/@value").extract_first()
    }
    #3. 发送登录请求post
    yield scrapy.FormRequest(login_url, formdata=formdata, callback=self.parse_login)
  def parse_login(self, response):
    #4.访问目标页面
    member_url="https://www.xxx.com/member"
    yield scrapy.Request(member_url, callback=self.parse_member)
  def parse_member(self, response):
    with open("02login.html",'wb') as f:
      f.write(response.body)

import scrapy
class LoginSpider(scrapy.Spider):
  name='login_code2'
  allowed_domains = ['xxx.com']
  #1. 登录页面
  start_urls = ['https://www.xxx.com/login/']
  def parse(self, response):
    #2. 代码登录
    login_url='https://www.xxx.com/login'
    formdata={
      "username":"xxx",
      "pwd":"xxx"
    }
    #3. 发送登录请求post
    yield scrapy.FormRequest.from_response(
      response,
      formxpath="//*[@id='login_pc']",
      formdata=formdata,
      method="POST", #覆盖之前的get请求
      callback=self.parse_login
    )
  def parse_login(self, response):
    #4.访问目标页面
    member_url="https://www.xxx.com/member"
    yield scrapy.Request(member_url, callback=self.parse_member)
  def parse_member(self, response):
    with open("03login.html",'wb') as f:
      f.write(response.body)