I actually shivered a little bit thinking about an app where each url was in a new file somewhere. I mean, ack is only going to take you so far when you're trying to find out where something was implemented.
And that's to say nothing of URL passing between different URL paths.
Honestly, Django doesn't have an index.py file anywhere. Rather it has a urls.py and apart from some really gnarly projects, if you wanna know where something is implemented, you open the root urls.py file and follow the chain down to the app where your URL is being generated. That points you at a view and usually the form or model that's causing issues.