Scrapy如何使用Loader忽略带有空白字段的项目

Question

我想知道如何忽略不填充所有字段的项目,某种丢弃,因为在scrapyd的输出中我得到的页面没有填满所有字段.

我有那个代码:

class Product(scrapy.Item):
    source_url = scrapy.Field(
        output_processor = TakeFirst()
    )
    name = scrapy.Field(
        input_processor = MapCompose(remove_entities),
        output_processor = TakeFirst()
    )
    initial_price = scrapy.Field(
        input_processor = MapCompose(remove_entities, clear_price),
        output_processor = TakeFirst()
    )
    main_image_url = scrapy.Field(
        output_processor = TakeFirst()
    )

分析器:

def parse_page(self, response):
    try:
        l = ItemLoader(item=Product(), response=response)
        l.add_value('source_url', response.url)
        l.add_css('name', 'h1.title-product::text')
        l.add_css('main_image_url', 'div.pics a img.zoom::attr(src)')

        l.add_css('initial_price', 'ul.precos li.preco_normal::text')
        l.add_css('initial_price', 'ul.promocao li.preco_promocao::text')

        return l.load_item()

    except Exception as e:
        print self.log("#1 ERRO: %s" % e), response.url

我想用Loader做它而不需要用我自己的Selector创建(避免两次处理项目).我想我可以将它们放到管道中,但可能不是最好的方法,因为这些项目无效.

Answer 1

验证数据是管道的典型用例之一.在您的情况下,您只需要编写一些少量代码来检查必需的字段,类似于:

from scrapy.exceptions import DropItem

class YourPersonalPipeline(object):
    def process_item(self, item, spider):
        required_fields = [] # your list of required fields
        if all(field in item for field in required_fields):
            return item
        else:
            raise DropItem("your reason")

您需要在settings.py中启用管道.阅读scrapy docs中的更多内容.