title: Portia/Scrapy - how to replace or add values to output JSON
body: <p>just 2 quick doubts: </p>
  
  <p>1- I want my final JSON file to replace the text extract (for example text extracted is ADD TO CART but I want to change to IN STOCK in my final JSON. Is it possible?</p>
  
  <p>2- I also would like to add some custom data to my final JSON file that is not in the website, for example "Store name"... so every product that I scrape will have the store name after it. Is it possible?</p>
  
  <p>I am using both Portia and Scrapy so your suggestions are welcome in both platforms.</p>
  
  <p>My Scrapy spider code is below:</p>
  
  <pre><code>import scrapy
  from __future__ import absolute_import
  from scrapy import Request
  from scrapy.linkextractors import LinkExtractor
  from scrapy.loader import ItemLoader
  from scrapy.loader.processors import Identity
  from scrapy.spiders import Rule
  from ..utils.spiders import BasePortiaSpider
  from ..utils.starturls import FeedGenerator, FragmentGenerator
  from ..utils.processors import Item, Field, Text, Number, Price, Date, Url, 
  Image, Regex
  from ..items import PortiaItem
  
  
  class Advent(BasePortiaSpider):
      name = "advent"
      allowed_domains = [u'www.adventgames.com.au']
      start_urls = [u'http://www.adventgames.com.au/c/4504822/1/all-games-a---k.html',
                    {u'url': u'http://www.adventgames.com.au/Listing/Category/?categoryId=4504822&amp;page=[1-5]',
                     u'fragments': [{u'valid': True,
                                     u'type': u'fixed',
                                     u'value': u'http://www.adventgames.com.au/Listing/Category/?categoryId=4504822&amp;page='},
                                    {u'valid': True,
                                     u'type': u'range',
                                     u'value': u'1-5'}],
                     u'type': u'generated'}]
      rules = [
          Rule(
              LinkExtractor(
                  allow=('.*'),
                  deny=()
              ),
              callback='parse_item',
              follow=True
          )
      ]
      items = [
          [
              Item(
                  PortiaItem,
                  None,
                  u'.DataViewCell &gt; form &gt; table',
                  [
                      Field(
                          u'Title',
                          'tr:nth-child(1) &gt; td &gt; .DataViewItemProductTitle &gt; a *::text',
                          []),
                      Field(
                          u'Price',
                          'tr:nth-child(1) &gt; td &gt; .DataViewItemOurPrice *::text',
                          []),
                      Field(
                          u'Img_src',
                          'tr:nth-child(1) &gt; td &gt; .DataViewItemThumbnailImage &gt; div &gt; a &gt; img::attr(src)',
                          []),
                      Field(
                          u'URL',
                          'tr:nth-child(1) &gt; td &gt; .DataViewItemProductTitle &gt; a::attr(href)',
                          []),
                      Field(
                          u'Stock',
                          'tr:nth-child(2) &gt; td &gt; .DataViewItemAddToCart &gt; .wButton::attr(value)',
                          [])])]]
  </code></pre>