Even if you have access to the entire source code of a Django site, figuring out how it works across various apps can be daunting. It is often best to start from the root urls.py URLconf file since it is literally a map that ties every request to the respective views.

With normal Python programs, I often start reading from the start of its execution—say, from the top-level main module or wherever the __main__ check idiom starts. In the case of Django applications, I usually start with urls.py since it is easier to follow the flow of execution based on various URL patterns a site has.

In Linux, you can use the following find command to locate the settings.py file and the corresponding line specifying the root urls.py:

$ find . -iname settings.py -exec grep -H 'ROOT_URLCONF' {} \;
./projectname/settings.py:ROOT_URLCONF = 'projectname.urls'

$ ls projectname/urls.py
projectname/urls.py