items.py文件

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

class DmozItem (scrapy.Item):
title= scrapy.Field()
link=scrapy.Field()
desc=scrapy.Fieldd()

dmo_spider.py文件

import scrapy

from tutorial.items import DmozItem

class DmozSpider(scrapy.Spider):
name = "dmoz"
allowed_domains = ["dmoz.org"]
start_urls = [
" http://www.dmoz.org/Computers/Programming/Languages/Python/Books/ ",
" http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/ "
]
def parse(self, response):
for sel in response.xpath('//ul/li'):
item = DmozItem()
item['title']= sel.xpath('a/text()').extract()
item['ink'] = sel.xpath('a/@href').extract()
item['desc']= sel.xpath('text()').extract()
yield item
为什么在dmzo_spider.py文件加入

from tutorial.items import DmozItem

执行scrapy crawl dmoz -o items.json时会报错，
如果去掉的话就会有 item = DmozItem()
exceptions.NameError: global name 'DmozItem' is not defined
的报错