Agreed about reading random source code files. I popped open the first .py file I found on the django project and got this:

conf.py

which I would say is a little esoteric for even the most precocious non-programmers.

But I also agree that investigating one's programming aptitude is a great low-investment high-reward endeavor. It does seem to be the case that many people just "get it". This thread offers some great suggestions on how to check: Checking for the Programming Gear.