Python 2.7 使用scrapy填写两阶段登录

登录后，我正在尝试刮除lynda.com。Lynda.com有一个两步验证过程，我必须输入用户名，然后输入密码。 看了这个之后，我创建了下面的spider，其中我创建了两个函数，一个用于插入用户名，另一个用于插入密码

# -*- coding: utf-8 -*-

import scrapy
from loginform import fill_login_form

class LyndaSpider(scrapy.Spider):
    name = 'lynda'

    start_urls = [
        'lynda.com'
    ]

    username_url = 'https://www.lynda.com/signin'

    login_user = '*****@gmail.com'
    login_password = '****'

    def start_requests(self):
        # let's start by sending a first request to login page
        yield scrapy.Request(self.username_url, self.parse_username_login)

    def parse_username_login(self, response):
        # got the username page, let's fill the login form...
        data, url, method = fill_login_form(response.url, response.body,
                                            username=self.login_user, password='')

        # ... and send a request with our login data
        return scrapy.http.FormRequest(url, formdata=dict(data),
                           method=method, callback=self.parse_password_login)

    def parse_password_login(self, response):
        # got the username page, let's fill the login form...
        data, url, method = fill_login_form(response.url, response.body, username='',
                                            password=self.login_password)

        # ... and send a request with our login data
        return scrapy.http.FormRequest(url, formdata=dict(data),
                                       method=method, callback=self.start_crawl)

    def start_crawl(self, response):
        # OK, we're in, let's start crawling the protected pages
        for url in self.start_urls:
            yield scrapy.Request(url)

    def parse(self, response):
        # do stuff with the logged in response
        pass

我得到以下错误：

Traceback (most recent call last):
  File "/home/edhiraj/program_files/venv2/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 653, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "/home/edhiraj/program_files/PycharmProjects/justin/justin/spiders/lynda_spider.py", line 25, in parse_username_login
    username=self.login_user, password='')
  File "/home/edhiraj/program_files/venv2/local/lib/python2.7/site-packages/loginform.py", line 80, in fill_login_form
    form.fields[passfield] = password
  File "/home/edhiraj/program_files/venv2/local/lib/python2.7/site-packages/lxml/html/__init__.py", line 1150, in __setitem__
    self.inputs[item].value = value
  File "/home/edhiraj/program_files/venv2/local/lib/python2.7/site-packages/lxml/html/__init__.py", line 1216, in __getitem__
    "No input element with the name %r" % name)
KeyError: 'No input element with the name None'

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为什么不使用FormRequest.from_response（）@Verz1Lka谢谢。我是新来的，所以我不知道