模拟登陆时，必须保证settings.py里的 COOKIES_ENABLED (Cookies中间件) 处于开启状态，COOKIES_ENABLED = True 或 # COOKIES_ENABLED = False，使用Scrapy模拟登陆简单易懂，可以说能处理大部分的登录操作。
一、策略一：直接POST数据
只要是需要提供post数据的，就可以用这种方法

# -*- coding: utf-8 -*-
import scrapy
class Renren1Spider(scrapy.Spider):
    name = "renren"
    allowed_domains = ["renren.com"]

    def start_requests(self):
        url = 'http://www.renren.com/PLogin.do'
        # FormRequest 是Scrapy发送POST请求的方法
        yield scrapy.FormRequest(
                url = url,
                formdata = {"email" : "xxx@163.com", "password" : "xxx"},
                callback = self.parse_page)

     def parse_page(self, response):
         with open("renren.html", "w") as filename:
             filename.write(response.body)

二、策略二：正规的模拟登陆步骤

① 首先发送登录页面的get请求，获取到页面里的登录必须的参数（比如说zhihu登陆界面的 _xsrf）
② 然后和账户密码一起post到服务器，登录成功

# -*- coding: utf-8 -*-
import scrapy

class Renren2Spider(scrapy.Spider):
    name = "renren"
    allowed_domains = ["renren.com"]
    start_urls = (
        "http://www.renren.com/PLogin.do",
    )

    # 处理start_urls里的登录url的响应内容，提取登陆需要的参数（如果需要的话)
    def parse(self, response):
        # 提取登陆需要的参数
        #_xsrf = response.xpath("//_xsrf").extract()[0]
        # 发送请求参数，并调用指定回调函数处理
        yield scrapy.FormRequest.from_response(
                response,
                formdata = {"email" : "xxx@163.com", "password" : "xxx"}, "_xsrf" = _xsrf},
                callback = self.parse_page
            )

    # 获取登录成功状态，访问需要登录后才能访问的页面
    def parse_page(self, response):
        url = "http://www.renren.com/422167102/profile"
        yield scrapy.Request(url, callback = self.parse_newpage)

    # 处理响应内容
    def parse_newpage(self, response):
        with open("renren.html", "w") as filename:
            filename.write(response.body)

三、策略三：使用保存登陆状态的Cookie模拟登陆

这种方法模拟登录成功率100%

# -*- coding: utf-8 -*-
import scrapy

class RenrenSpider(scrapy.Spider):
    name = "renren"
    allowed_domains = ["renren.com"]
    start_urls = (
        'http://www.renren.com/hahaha',
        'http://www.renren.com/meinv',
        'http://www.renren.com/shuaige',
    )

    cookies = {
    "anonymid" : "ixrna3fysufnwv",
    "_r01_" : "1",
    "ap" : "327550029",
    "JSESSIONID" : "abciwg61A_RvtaRS3GjOv",
    "depovince" : "GW",
    "springskin" : "set",
    "jebe_key" : "f6fb270b-d06d-42e6-8b53-e67c3156aa7e%7Cc13c37f53bca9e1e7132d4b58ce00fa3%7C1484060607478%7C1%7C1486198628950",
    "t" : "691808127750a83d33704a565d8340ae9",
    "societyguester" : "691808127750a83d33704a565d8340ae9",
    "id" : "327550029",
    "xnsid" : "f42b25cf",
    "loginfrom" : "syshome"
    }

    # 可以重写Spider类的start_requests方法，附带Cookie值，发送POST请求
    def start_requests(self):
        for url in self.start_urls:
            yield scrapy.FormRequest(url, cookies = self.cookies, callback = self.parse_page)

    # 处理响应内容
    def parse_page(self, response):
        with open("deng.html", "w") as filename:
            filename.write(response.body)