Not really a bad practice, more of a personal style choice. The concerns here aren't any more mixed than if you created a views.py and sub-classed the generic

Not really a bad practice, more of a personal style choice. The concerns here aren't any more mixed than if you created a views.py and sub-classed the generic views settings your own options. urls.py just maps patterns to views, it's just in this case you're setting several options on some generic views. That being said, I almost always DO separate them because over time your generic views often become more complex and more overridden. I also personally prefer my urls.py to not get so "messy", but it's not really a horrible practice or one with a lot of downsides.