How to pass data from start_requests to parse callbacks in scrapy?

To transfer data to the scrape callback from the initial start_requests() method the Request.meta attribute can be used:

import scrapy

class MySpider(scrapy.Spider):
    name = 'myspider'

    def start_requests(self):
        urls = [...]
        for index, url in enumerate(urls):
            yield scrapy.Request(url, meta={'index':index})

    def parse(self, response):
        print(response.url)
        print(response.meta['index'])

In the example above we are using Request.meta parameter and pass the index of URL that has been scheduled to be scraped.