擅长:python、mysql、java
<p><strong>更新</strong>来自注释:看起来<a href="https://doc.scrapy.org/en/latest/topics/loaders.html#nested-loaders" rel="nofollow noreferrer">nested loaders</a>是更新的方法。另一条评论指出,这种方法在序列化期间会导致错误。在</p>
<p>最好的方法是创建<code>main</code>和<code>meta</code>项类/装入器。在</p>
<pre><code>from scrapy.item import Item, Field
from scrapy.contrib.loader import ItemLoader
from scrapy.contrib.loader.processor import TakeFirst
class MetaItem(Item):
url = Field()
added_on = Field()
class MainItem(Item):
price = Field()
title = Field()
meta = Field(serializer=MetaItem)
class MainItemLoader(ItemLoader):
default_item_class = MainItem
default_output_processor = TakeFirst()
class MetaItemLoader(ItemLoader):
default_item_class = MetaItem
default_output_processor = TakeFirst()
</code></pre>
<p>示例用法:</p>
^{pr2}$
<p>之后,您可以通过创建更多的“子项”在将来轻松扩展项</p>