How to disable cache in scrapy?

Cache can be disable in 2 ways

1. Changing values in cache related settings in setting.py file. By Keeping HTTPCACHE_ENABLED=False
2. Or it can be done in runtime " scrapy crawl crawl-name --set HTTPCACHE_ENABLED=False

Here I assume that you just want to avoid caching only specific requests.

For this example it means avoid caching those requests under start_requests and cache all other requests (which you may have under parseResponse).

To do this just add productResponse.meta['dont_cache'] = True line to your code and set HTTPCACHE_ENABLED=True under settings.py

Now all other requests will be cached.

def start_requests(self):
        meta = {'REDIRECT_ENABLED':True}
        productUrl = "http://xyz"
        cookies = [{'name': '', 'value': '=='},{'name': '', 'value': '=='}]
        for cook in cookies:

            header = {"User-Agent":"Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.85 Safari/537.36"}
            productResponse = scrapy.Request(productUrl,callback=self.parseResponse,method='GET',
                                             meta=meta,body=str(),cookies=[cook],
                                             encoding='utf-8',priority=0,dont_filter=True)
            productResponse.meta['dont_cache'] = True
            yield productResponse

def parseResponse(self,response): 
     selector = Selector(response)
     print selector.xpath("xpaths here").extract()
     yield None