Items有哪些知识?
1、声明
import scrapy class Product(scrapy.Item): name = scrapy.Field() price = scrapy.Field() stock = scrapy.Field() last_updated = scrapy.Field(serializer=str)
2、创建item
>>> product = Product(name='Desktop PC', price=1000) >>> print product Product(name='Desktop PC', price=1000)
3、dict API
>>> product.keys() ['price', 'name'] >>> product.items() [('price', 1000), ('name', 'Desktop PC')]
4、复制item
product3 = product2.copy()
5、扩展Item(继承)
class DiscountedProduct(Product): discount_percent = scrapy.Field(serializer=str) discount_expiration_date = scrapy.Field()
怎么使用持久化?这章没讲,看下面内容吧!