title: python scrapy parse() function, where is the return value returned to?
body: <p>I am new on Scrapy, and I am sorry if this question is trivial. I have read the document on Scrapy from official webpage. And while I look through the document, I met this example:</p>
  
  <pre><code>import scrapy
  from myproject.items import MyItem
  
  class MySpider(scrapy.Spider):
    name = ’example.com’
    allowed_domains = [’example.com’]
    start_urls = [
    ’http://www.example.com/1.html’,
    ’http://www.example.com/2.html’,
    ’http://www.example.com/3.html’,
    ]
  
    def parse(self, response):
      for h3 in response.xpath(’//h3’).extract():
        yield MyItem(title=h3)
      for url in response.xpath(’//a/@href’).extract():
        yield scrapy.Request(url, callback=self.parse) 
  </code></pre>
  
  <p>I know, the parse method must return an item or/and request, but where are these return values returned to?</p>
  
  <p>One is an item and the other is request, I think these two type would be handled differently  and in the case of <code>CrawlSpider</code>, it has Rule with callback. What about this callback's return value? where to ? same as <code>parse()</code>?</p>
  
  <p>I am very confused on Scrapy procedure, even i read the document....</p>