老师，你好！向你请教几个问题

1.在使用selenium已成功登录知乎后，想提取all_urls，进行debug时无法跳转到parse函数，代码会重新执行start_requestion函数进行登录，这时会报无法找到登录界面切换密码登录的元素而终止：raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.NoSuchElementException: Message: no such element: Unable to locate element: {“method”:“xpath”,“selector”:"//div[@class=“SignFlow-tabs”]/div[2]"}
(Session info: chrome=86.0.4240.111)

2.我尝试使用try expect 语句将初始登录的代码写到expect中去，在已登录成功知乎的情况下在debug，也无法成功，报如下错误：
2020-11-27 01:34:28 [selenium.webdriver.remote.remote_connection] DEBUG: Finished Request
Unhandled error in Deferred:
2020-11-27 01:34:30 [twisted] CRITICAL: Unhandled error in Deferred:

Traceback (most recent call last):
File “C:\Python\lib\site-packages\scrapy\crawler.py”, line 177, in crawl
return self._crawl(crawler, *args, **kwargs)
File “C:\Python\lib\site-packages\scrapy\crawler.py”, line 181, in _crawl
d = crawler.crawl(*args, **kwargs)
File “C:\Python\lib\site-packages\twisted\internet\defer.py”, line 1613, in unwindGenerator
return _cancellableInlineCallbacks(gen)
File “C:\Python\lib\site-packages\twisted\internet\defer.py”, line 1529, in _cancellableInlineCallbacks
_inlineCallbacks(None, g, status)
— —
File “C:\Python\lib\site-packages\twisted\internet\defer.py”, line 1418, in _inlineCallbacks
result = g.send(result)
File “C:\Python\lib\site-packages\scrapy\crawler.py”, line 90, in crawl
start_requests = iter(self.spider.start_requests())
builtins.TypeError: ‘NoneType’ object is not iterable

2020-11-27 01:34:30 [twisted] CRITICAL:
Traceback (most recent call last):
File “C:\Python\lib\site-packages\twisted\internet\defer.py”, line 1418, in _inlineCallbacks
result = g.send(result)
File “C:\Python\lib\site-packages\scrapy\crawler.py”, line 90, in crawl
start_requests = iter(self.spider.start_requests())
TypeError: ‘NoneType’ object is not iterable

3.我尝试先退出知乎登录，然后再debug发现可以进入parse函数并成功返回了url值

如果每次debug时都要退出手动知乎后再进行其它操作就显得如此“笨比”，反复思考后认为操作2中的逻辑没有问题，但debug始终无法进入parse函数，多次尝试无果后请教老师，后续代码是哪里出了问题？
代码如下：`# -- coding: utf-8 --

class ZhihuSpider(scrapy.Spider):
name = 'zhihu’
allowed_domains = [‘www.zhihu.com’]
start_urls = [‘https://www.zhihu.com/’]

headers = {
    "HOST": "www.zhihu.com",
    "Referer": "https://www.zhizhu.com",
    'User-Agent': "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36"
}

def start_question(self):
    pass

def parse_answer(self):
    pass

def parse(self, response):
    # cookie_dict = response.meta.get('cookies')
    all_urls = response.css('a::attr(href)').extract()
    all_urls = [parse.urljoin(response.url, url) for url in all_urls]
    for url in all_urls:
        print(url)

def start_requests(self):

    # 知乎存在反爬，使用selenium驱动Chromedriver模拟登录
    chrome_option = Options()
    chrome_option.add_argument('--disable-extensions')
    chrome_option.add_experimental_option('debuggerAddress', '127.0.0.1:9222')

    # 指定Chrome浏览器绝对路径，否则会报浏览器启动路径错误
    option_location = webdriver.ChromeOptions()
    option_location.binary_location = r'F:/Google/Application/chrome.exe'
    browser = webdriver.Chrome(executable_path='E:/Scrapy code/zhihu/chromedriver.exe', options=option_location,
                               chrome_options=chrome_option)
    try:
        browser.maximize_window()
    except:
        pass
    browser.get('https://www.zhihu.com/signin')

    # 若find_element_by_xpath/css().click()方法失效时使用获取屏幕坐标切换登录方式
    # move(725, 280)
    # click()
    login_sign = False
    try:
        sign_success = browser.find_element_by_class_name('AppHeader-profile')
        login_sign = True
    except:

        browser.find_element_by_xpath('//div[@class="SignFlow-tabs"]/div[2]').click()
        time.sleep(1)

        # 若出现重复添加用户名和密码，则使用下语句
        # browser.find_element_by_css_selector('.SignFlow-accountInput.Input-wrapper input').send_keys(Keys.CONTROL + 'a')
        browser.find_element_by_css_selector('.SignFlow-accountInput.Input-wrapper input').send_keys('15898518817')
        time.sleep(1)
        # browser.find_element_by_css_selector('.SignFlow-password input').send_keys(Keys.CONTROL+'a')
        browser.find_element_by_css_selector('.SignFlow-password input').send_keys('12345678ggg')
        time.sleep(1)
        # 启动登录按钮，.click()方法失效时使用
        # move(730, 522)
        # click()
        browser.find_element_by_css_selector('.Button.SignFlow-submitButton').click()
    time.sleep(2)
    # login_sign = False
    while not login_sign:
        try:
            sign_success = browser.find_element_by_class_name('AppHeader-profile')
            login_sign = True
        except:
            pass
        try:
            english_captcha_element = browser.find_element_by_class_name('Captcha-englishImg')
        except:
            english_captcha_element = None
        try:
            chinese_captcha_element = browser.find_element_by_class_name('Captcha-chineseImg')
        except:
            chinese_captcha_element = None

        if chinese_captcha_element:
            base64_text = chinese_captcha_element.get_attribute('src')
            element_relative = chinese_captcha_element.location
            x_relative = element_relative['x']
            y_relative = element_relative['y']
            browser_opposite = browser.execute_script('return window.outerHeight - window.innerHeight;')
            code = base64_text.replace('data:image/jpg;base64,', '').replace('%0A', '')
            fh = open('yzm_cn.jpeg', 'wb')
            fh.write(base64.b64decode(code))
            fh.close()

            z = zheye()
            positions = z.Recognize('yzm_cn.jpeg')
            last_position = []
            if len(positions) == 1:
                last_position.append([positions[0][1], positions[0][0]])
                move(x_relative + int(last_position[0][0]/2), y_relative + int(last_position[0][1]/2) + browser_opposite)
                time.sleep(1)
                click()
            else:
                if positions[0][1] > positions[1][1]:
                    last_position.append([positions[1][1], positions[1][0]])
                    last_position.append([positions[0][1], positions[0][0]])
                else:
                    last_position.append([positions[0][1], positions[0][0]])
                    last_position.append([positions[1][1], positions[1][0]])
                first_position = [int(last_position[0][0] / 2), int(last_position[0][1] / 2)]
                second_position = [int(last_position[1][0] / 2), int(last_position[1][1] / 2)]
                move(x_relative+first_position[0], y_relative+first_position[1]+browser_opposite)
                time.sleep(1)
                click()
                move(x_relative+second_position[0], y_relative+second_position[1]+browser_opposite)
                time.sleep(1)
                click()
            print(last_position)

            browser.find_element_by_css_selector('.SignFlow-accountInput.Input-wrapper input').send_keys(Keys.CONTROL + 'a')
            browser.find_element_by_css_selector('.SignFlow-accountInput.Input-wrapper input').send_keys('15898518817')
            time.sleep(1)
            browser.find_element_by_css_selector('.SignFlow-password input').send_keys(Keys.CONTROL + 'a')
            browser.find_element_by_css_selector('.SignFlow-password input').send_keys('12345678gg')
            time.sleep(1)
            browser.find_element_by_css_selector('.Button.SignFlow-submitButton').click()

        if english_captcha_element:
            base64_text = english_captcha_element.get_attribute('src')
            code = base64_text.replace('data:image/jpg;base64,', '').replace('%0A', '')
            fh = open('yzm_en.jpeg', 'wb')
            fh.write(base64.b64decode(code))
            fh.close()
            cjy = chaojiying.Chaojiying_Client('personal', '123456789', '910064')
            im = open('yzm_en.jpeg', 'rb').read()
            js_dict = cjy.PostPic(im, 1902)
            en_yzm = js_dict['pic_str']

            while True:
                if en_yzm == '':
                    en_yzm = cjy.PostPic(im, 1906)['pic_str']
                else:
                    break
            time.sleep(2)
            browser.find_element_by_xpath('//div[@class="Captcha SignFlow-captchaContainer"]/div/div/label/input').send_keys(Keys.CONTROL + 'a')
            browser.find_element_by_xpath('//div[@class="Captcha SignFlow-captchaContainer"]/div/div/label/input').send_keys(en_yzm)
            time.sleep(1)
            browser.find_element_by_css_selector('.SignFlow-accountInput.Input-wrapper input').send_keys(
                Keys.CONTROL + 'a')
            browser.find_element_by_css_selector('.SignFlow-accountInput.Input-wrapper input').send_keys(
                '15898518817')
            time.sleep(1)
            browser.find_element_by_css_selector('.SignFlow-password input').send_keys(Keys.CONTROL + 'a')
            browser.find_element_by_css_selector('.SignFlow-password input').send_keys('12345678gg')
            time.sleep(1)
            browser.find_element_by_css_selector('.Button.SignFlow-submitButton').click()

        time.sleep(3)
        try:
            sign_success = browser.find_element_by_class_name("AppHeader-profile")
            login_sign = True

            cookies = browser.get_cookies()
            pickle.dump(cookies, open('E:/Scrapy code/zhihu/zhihu_article/cookies/zhihu.cookie', 'wb'))
            cookie_dict = {}
            for cookie in cookies:
                cookie_dict[cookie['name']] = cookie['value']

            browser.close()
            return [scrapy.Request(url=self.start_urls[0], dont_filter=True, cookies=cookie_dict, headers=self.headers)]
        except:
            pass

4.由于个人水平属实菜的离谱，观看爬取知乎这一章很费劲，加上知乎几经更改已和原视频的一些章节内容存在差距，动手起来大部分时间都在排错找错，希望能向老师提个建议，补录一两个视频用于知乎这章的前后新旧内容衔接，也能方便后续同学看到这里时能快速上手，谢谢老师！