python - Scrapy KeyError while using pipeline -

can explain me why error? didn't it. try store extracted data database via scrapy pipeline, worked project following error:

traceback (most recent call last):       file "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 588, in _runcallbacks         current.result = callback(current.result, *args, **kw)       file "/home/darknet/darknet/pipelines.py", line 11, in process_item         length = range(len(item['quantity']))       file "/usr/lib/python2.7/dist-packages/scrapy/item.py", line 56, in __getitem__         return self._values[key]     keyerror: 'quantity' 

my pipeline:

import darknet darknet.items import darknetitem models import db models import blackmarket   class mysqlpipeline(object):      def process_item(self, item, spider):          length = range(len(item['quantity']))         x in length:             record = blackmarket(product=item['product'][x], quantity=item['quantity'][x], price=item['price'][x])             db.add(record)             db.commit()         return item 

i use items in code snippet:

item = darknetitem() item['product'] = response.xpath('//div[@class="text otitle"]/a/text()').extract() item['price'] = response.xpath('//div[@class="bottom oprice"]/text()').extract() item['quantity'] = response.xpath('//div[@class="text otitle"]/a/text()').extract() yield item