Scrapy Crawl 运行出错 AttributeError: 'xxxSpider' object has no attribute '_rules' 的问题解决

按照官方的文档写的demo，只是多了个init函数，最终执行时提示没有_rules这个属性的错误日志如下：

 ......
  File "C:\ProgramData\Anaconda3\lib\site-packages\scrapy\spiders\crawl.py", line 82, in _parse_response
    for request_or_item in self._requests_to_follow(response):
  File "C:\ProgramData\Anaconda3\lib\site-packages\scrapy\spiders\crawl.py", line 60, in _requests_to_follow
    for n, rule in enumerate(self._rules):
AttributeError: 'TestSpider' object has no attribute '_rules'

出问题的spider代码如下：

# -*- coding: utf-8 -*-
import scrapy
from scrapy.linkextractors import LinkExtractor
from scrapy.spiders import CrawlSpider, Rule
from newtest.items import NewtestItem


class TestSpider(CrawlSpider):
    
    def __init__(self,*args, **kwargs):
        self.headers = {
            'Content-Type':'application/x-www-form-urlencoded; charset=UTF-8',
            'Accept-Encoding':'gzip, deflate',
            'User-Agent':'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36'
        }

    name = 'test'
    allowed_domains = ['example.com']
    start_urls = ['http://www.example.com']

    rules = (
        # Extract links matching 'category.php' (but not matching 'subsection.php')
        # and follow links from them (since no callback means follow=True by default).
        Rule(LinkExtractor(allow=('category\.php', ), deny=('subsection\.php', ))),

        # Extract links matching 'item.php' and parse them with the spider's method parse_item
        Rule(LinkExtractor(allow=('item\.php', )), callback='parse_item'),
    )

    def parse_item(self, response):
        self.logger.info('Hi, this is an item page! %s', response.url)
        item = scrapy.Item()
        item['id'] = response.xpath('//td[@id="item_id"]/text()').re(r'ID: (\d+)')
        item['name'] = response.xpath('//td[@id="item_name"]/text()').extract()
        item['description'] = response.xpath('//td[@id="item_description"]/text()').extract()
        return item

后来仔细看了下，跟官方不一样的就是自己重写了init初始化方法，而根据这个提示的日志，应该是覆盖了CrawlSpider的init方法但是没有调用父类的init导致_rules这个属性没有声明导致的。我们来看下CrawlSpider的源码：


所以如果我们的Spider是从CrawlSpider继承过来的，并且自己需要实现__init__ 方法的话，记住要调用父类的__init__方法保障能正常初始化crawlspider的属性。
修改后的代码如下：

第11行的super(TestSpider, self).__init__(*args, **kwargs) 是关键：

# -*- coding: utf-8 -*-
import scrapy
from scrapy.linkextractors import LinkExtractor
from scrapy.spiders import CrawlSpider, Rule
from newtest.items import NewtestItem


class TestSpider(CrawlSpider):
    
    def __init__(self, *args, **kwargs):
        super(TestSpider, self).__init__(*args, **kwargs)  # 这里是关键
        self.headers = {
            'Content-Type':'application/x-www-form-urlencoded; charset=UTF-8',
            'Accept-Encoding':'gzip, deflate',
            'User-Agent':'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36'
        }

    name = 'test'
    allowed_domains = ['example.com']
    start_urls = ['http://www.example.com']

    rules = (
        # Extract links matching 'category.php' (but not matching 'subsection.php')
        # and follow links from them (since no callback means follow=True by default).
        Rule(LinkExtractor(allow=('category\.php', ), deny=('subsection\.php', ))),

        # Extract links matching 'item.php' and parse them with the spider's method parse_item
        Rule(LinkExtractor(allow=('item\.php', )), callback='parse_item'),
    )

    def parse_item(self, response):
        self.logger.info('Hi, this is an item page! %s', response.url)
        item = scrapy.Item()
        item['id'] = response.xpath('//td[@id="item_id"]/text()').re(r'ID: (\d+)')
        item['name'] = response.xpath('//td[@id="item_name"]/text()').extract()
        item['description'] = response.xpath('//td[@id="item_description"]/text()').extract()
        return item