ComicSpider | Web comic downloader and viewer | Download Utils library

I'm using Scrapy to crawl a set of similar pages (webcomics). Because these pages are very similar, I wrote a class called ComicCrawler which contains all the spider logic and some class variables (start_url, next_selector, etc.). I then override these class variables in concrete classes for each spider.

Manually creating classes for each comic is cumbersome. I now want to specify the attributes in a JSON file and create the classes during runtime (ie. apply the factory pattern (?)) How do I best go about that?

Alternatively: Is there a way to run a spider without creating a class for it? Edit: The core problem seems to be that Scrapy uses classes, not instances for its spiders. Otherwise I'd just make the class variables instance variables and be done with it.

Example: