Scrapy：登录后抓取下一页

Question

我对网络垃圾很陌生。成功登录quotes.toscrape.com网站后，我正在尝试抓取页面。我的代码（scrapytest/spider/quotes\u spider.py）如下所示：

import scrapy
from scrapy.http import FormRequest
from ..items import ScrapytestItem
from scrapy.utils.response import open_in_browser
from scrapy.spiders.init import InitSpider


class QuoteSpider(scrapy.Spider):
    name = 'scrapyquotes'
    login_url = 'http://quotes.toscrape.com/login'
    start_urls = [login_url]

    def parse(self,response):
        token = response.css('input[name="csrf_token"]::attr(value)').extract_first()
        yield scrapy.FormRequest(url=self.login_url,formdata={
            'csrf_token':token,
            'username':'roberthng',
            'password':'dsadsadsa'
        },callback = self.start_scraping)

    def start_scraping(self,response):
        items = ScrapytestItem()
        all_div_quotes=response.css('div.quote')

        for quotes in all_div_quotes:
            title = quotes.css('span.text::text').extract()
            author = quotes.css('.author::text').extract()
            tag = quotes.css('.tag::text').extract()

            items['title'] = title
            items['author'] = author
            items['tag'] = tag

            yield items

        #Go to Next Page:     
        next_page = response.css('li.next a::attr(href)').get()
        if next_page is not None:
            yield response.follow(next_page, callback=self.parse)

每当我在终端（VSC）上通过$scrapy crawl scrapyquotes运行这段代码时，这段代码只会刮到登录并刮到第一页。它总是无法爬到第二页。下面是出现的错误消息：

2020-10-10 12:26:42 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://quotes.toscrape.com/page/2/> (referer: http://quotes.toscrape.com/)

2020-10-10 12:26:42 [scrapy.core.scraper] ERROR: Spider error processing <GET http://quotes.toscrape.com/page/2/> (referer: http://quotes.toscrape.com/)

我怀疑这与start_URL有关，但当我将其更改为'http://quotes.toscrape.com/page/1“代码甚至连第一页都没有。有人能帮我解决这个问题吗？提前谢谢你

完整错误日志：

2020-10-10 12:26:40 [scrapy.utils.log] INFO: Scrapy 2.3.0 started (bot: scrapytest)
2020-10-10 12:26:40 [scrapy.utils.log] INFO: Versions: lxml 4.5.2.0, libxml2 2.9.10, cssselect 1.1.0, parsel 1.5.2, w3lib 1.21.0, Twisted 20.3.0, Python 3.8.3 (default, Jul  2 2020, 17:30:36) [MSC v.1916 64 bit (AMD64)], pyOpenSSL 19.1.0 (OpenSSL 1.1.1h  22 Sep 2020), cryptography 3.1.1, Platform Windows-10-10.0.18362-SP0 
2020-10-10 12:26:40 [scrapy.utils.log] DEBUG: Using reactor: twisted.internet.selectreactor.SelectReactor
2020-10-10 12:26:40 [scrapy.crawler] INFO: Overridden settings:
{'BOT_NAME': 'scrapytest',
 'NEWSPIDER_MODULE': 'scrapytest.spiders',
 'ROBOTSTXT_OBEY': True,
 'SPIDER_MODULES': ['scrapytest.spiders']}
2020-10-10 12:26:40 [scrapy.extensions.telnet] INFO: Telnet Password: 92d2fd08391e76a9
2020-10-10 12:26:40 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.corestats.CoreStats',
 'scrapy.extensions.telnet.TelnetConsole',
 'scrapy.extensions.logstats.LogStats']
2020-10-10 12:26:40 [scrapy.middleware] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',
 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
 'scrapy.downloadermiddlewares.retry.RetryMiddleware',
 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2020-10-10 12:26:40 [scrapy.middleware] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
 'scrapy.spidermiddlewares.referer.RefererMiddleware',
 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
 'scrapy.spidermiddlewares.depth.DepthMiddleware']
2020-10-10 12:26:40 [scrapy.middleware] INFO: Enabled item pipelines:
['scrapytest.pipelines.ScrapytestPipeline']
2020-10-10 12:26:40 [scrapy.core.engine] INFO: Spider opened
2020-10-10 12:26:40 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2020-10-10 12:26:40 [scrapy.extensions.telnet] INFO: Telnet console listening on 127.0.0.1:6023
2020-10-10 12:26:41 [scrapy.core.engine] DEBUG: Crawled (404) <GET http://quotes.toscrape.com/robots.txt> (referer: None)
2020-10-10 12:26:41 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://quotes.toscrape.com/login> (referer: None)
2020-10-10 12:26:41 [scrapy.downloadermiddlewares.redirect] DEBUG: Redirecting (302) to <GET http://quotes.toscrape.com/> from <POST http://quotes.toscrape.com/login>
2020-10-10 12:26:41 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://quotes.toscrape.com/> (referer: http://quotes.toscrape.com/login)
2020-10-10 12:26:41 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['Albert Einstein'],
 'tag': ['change', 'deep-thoughts', 'thinking', 'world'],
 'title': ['“The world as we have created it is a process of our thinking. It '
           'cannot be changed without changing our thinking.”']}
2020-10-10 12:26:41 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['J.K. Rowling'],
 'tag': ['abilities', 'choices'],
 'title': ['“It is our choices, Harry, that show what we truly are, far more '
           'than our abilities.”']}
2020-10-10 12:26:42 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['Albert Einstein'],
 'tag': ['inspirational', 'life', 'live', 'miracle', 'miracles'],
 'title': ['“There are only two ways to live your life. One is as though '
           'nothing is a miracle. The other is as though everything is a '
           'miracle.”']}
2020-10-10 12:26:42 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['Jane Austen'],
 'tag': ['aliteracy', 'books', 'classic', 'humor'],
 'title': ['“The person, be it gentleman or lady, who has not pleasure in a '
           'good novel, must be intolerably stupid.”']}
2020-10-10 12:26:42 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['Marilyn Monroe'],
 'tag': ['be-yourself', 'inspirational'],
 'title': ["“Imperfection is beauty, madness is genius and it's better to be "
           'absolutely ridiculous than absolutely boring.”']}
2020-10-10 12:26:42 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['Albert Einstein'],
 'tag': ['adulthood', 'success', 'value'],
 'title': ['“Try not to become a man of success. Rather become a man of '
           'value.”']}
2020-10-10 12:26:42 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['André Gide'],
 'tag': ['life', 'love'],
 'title': ['“It is better to be hated for what you are than to be loved for '
           'what you are not.”']}
2020-10-10 12:26:42 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['Thomas A. Edison'],
 'tag': ['edison', 'failure', 'inspirational', 'paraphrased'],
 'title': ["“I have not failed. I've just found 10,000 ways that won't work.”"]}
2020-10-10 12:26:42 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['Eleanor Roosevelt'],
 'tag': ['misattributed-eleanor-roosevelt'],
 'title': ['“A woman is like a tea bag; you never know how strong it is until '
           "it's in hot water.”"]}
2020-10-10 12:26:42 [scrapy.core.scraper] DEBUG: Scraped from <200 http://quotes.toscrape.com/>
{'author': ['Steve Martin'],
 'tag': ['humor', 'obvious', 'simile'],
 'title': ['“A day without sunshine is like, you know, night.”']}
2020-10-10 12:26:42 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://quotes.toscrape.com/page/2/> (referer: http://quotes.toscrape.com/)
2020-10-10 12:26:42 [scrapy.core.scraper] ERROR: Spider error processing <GET http://quotes.toscrape.com/page/2/> (referer: http://quotes.toscrape.com/)
Traceback (most recent call last):
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\utils\defer.py", line 120, in iter_errback
    yield next(it)
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\utils\python.py", line 347, in __next__
    return next(self.data)
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\utils\python.py", line 347, in __next__
    return next(self.data)
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\core\spidermw.py", line 64, in _evaluate_iterable
    for r in iterable:
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\spidermiddlewares\offsite.py", line 29, in process_spider_output
    for x in result:
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\core\spidermw.py", line 64, in _evaluate_iterable
    for r in iterable:
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\spidermiddlewares\referer.py", line 340, in <genexpr>
    return (_set_referer(r) for r in result or ())
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\core\spidermw.py", line 64, in _evaluate_iterable
    for r in iterable:
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\spidermiddlewares\urllength.py", line 37, in <genexpr>
    return (r for r in result or () if _filter(r))
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\core\spidermw.py", line 64, in _evaluate_iterable
    for r in iterable:
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\spidermiddlewares\depth.py", line 58, in <genexpr>
    return (r for r in result or () if _filter(r))
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\core\spidermw.py", line 64, in _evaluate_iterable
    for r in iterable:
  File "C:\Users\Robert\Documents\Demos\vstoolbox\scrapytest\scrapytest\spiders\quotes_spider.py", line 15, in parse
    yield scrapy.FormRequest(url=self.login_url,formdata={
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\http\request\form.py", line 31, in __init__
    querystr = _urlencode(items, self.encoding)
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\http\request\form.py", line 71, in _urlencode
    values = [(to_bytes(k, enc), to_bytes(v, enc))
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\http\request\form.py", line 71, in <listcomp>
    values = [(to_bytes(k, enc), to_bytes(v, enc))
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\utils\python.py", line 104, in to_bytes
    raise TypeError('to_bytes must receive a str or bytes '
TypeError: to_bytes must receive a str or bytes object, got NoneType
2020-10-10 12:26:42 [scrapy.core.engine] INFO: Closing spider (finished)
2020-10-10 12:26:42 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 1832,
 'downloader/request_count': 5,
 'downloader/request_method_count/GET': 4,
 'downloader/request_method_count/POST': 1,
 'downloader/response_bytes': 8041,
 'downloader/response_count': 5,
 'downloader/response_status_count/200': 3,
 'downloader/response_status_count/302': 1,
 'downloader/response_status_count/404': 1,
 'elapsed_time_seconds': 2.063919,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2020, 10, 10, 5, 26, 42, 486494),
 'item_scraped_count': 10,
 'log_count/DEBUG': 15,
 'log_count/ERROR': 1,
 'log_count/INFO': 10,
 'request_depth_max': 2,
 'response_received_count': 4,
 'robotstxt/request_count': 1,
 'robotstxt/response_status_count/404': 1,
 'scheduler/dequeued': 4,
 'scheduler/dequeued/memory': 4,
 'scheduler/enqueued': 4,
 'scheduler/enqueued/memory': 4,
 'spider_exceptions/TypeError': 1,
 'start_time': datetime.datetime(2020, 10, 10, 5, 26, 40, 422575)}
2020-10-10 12:26:42 [scrapy.core.engine] INFO: Spider closed (finished)

目录中其他文件的代码：

（scrapytest/items.py）

import scrapy
    
class ScrapytestItem(scrapy.Item):
#define the fields for your item here like:
title = scrapy.Field()
author = scrapy.Field()
tag = scrapy.Field()`

（scrapytest/pipelines.py）

from itemadapter import ItemAdapter
import sqlite3


class ScrapytestPipeline(object):        
    def __init__(self):
        self.create_connection()
        self.create_table()

    def create_connection(self):
        self.conn = sqlite3.connect('myquotes.db')
        self.curr = self.conn.cursor()
    
    def create_table(self):
        self.curr.execute("""DROP TABLE IF EXISTS quotes_tb""")
        self.curr.execute("""create table quotes_tb(
                            title text,
                            author text,
                            tag text
                            )""")

    def process_item(self, item, spider):
            self.store_db(item) 
            #print("Pipeline :" + item['title'][0])
            return item

    def store_db(self, item):
        self.curr.execute("""insert into quotes_tb values(?,?,?)""",(
            item['title'][0],
            item['author'][0],
            item['tag'][0]
        ))
        self.conn.commit()

（scrapytest/settings.py）

BOT_NAME = 'scrapytest'

SPIDER_MODULES = ['scrapytest.spiders']
NEWSPIDER_MODULE = 'scrapytest.spiders'
ITEM_PIPELINES = {
    'scrapytest.pipelines.ScrapytestPipeline': 300,
}

Answer 1

您将错误的函数传递到回调中，您的self.parse函数只能用于登录页面

if next_page is not None:
    yield response.follow(next_page, callback=self.start_scraping)

Answer 2

这来自您的执行日志：

  File "C:\Users\Robert\Documents\Demos\vstoolbox\scrapytest\scrapytest\spiders\quotes_spider.py", line 15, in parse
    yield scrapy.FormRequest(url=self.login_url,formdata={
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\http\request\form.py", line 31, in __init__
    querystr = _urlencode(items, self.encoding)
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\http\request\form.py", line 71, in _urlencode
    values = [(to_bytes(k, enc), to_bytes(v, enc))
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\http\request\form.py", line 71, in <listcomp>
    values = [(to_bytes(k, enc), to_bytes(v, enc))
  File "C:\Users\Robert\anaconda3\envs\condatest\lib\site-packages\scrapy\utils\python.py", line 104, in to_bytes
    raise TypeError('to_bytes must receive a str or bytes '
TypeError: to_bytes must receive a str or bytes object, got NoneType

简而言之，它告诉您formdata参数中的参数是None，但它应该是“str或bytes对象”。 假设formdata有三个字段，只有一个是变量，token必须返回空

    ...
    token = response.css('input[name="csrf_token"]::attr(value)').extract_first()
    yield scrapy.FormRequest(url=self.login_url,formdata={
        'csrf_token':token,
        'username':'roberthng',
        'password':'dsadsadsa'
    },callback = self.start_scraping)

但是，如果您在登录页面中，选择器将正确返回值。我的假设是，当您定义下一页的请求时，您正在将回调设置为parse方法（或者根本不设置它，这将导致parse作为默认值）。 我说的是假设，因为你没有发布代码的那一部分。您的代码示例到此为止：

    #Go to Next Page:     
    next_page = response.css('li.next a::attr(href)').get()
    if next_page is not None:

因此，请确保在此之后，为请求正确设置了回调函数