Take a look at the requirements.txt: https://github.com/qtile/qtile/blob/ecf216205ccfe72bbdee3183489ad0b67eef0100/requirements.txt https://github.com/qtile/qtil

Take a look at the requirements.txt: https://github.com/qtile/qtile/blob/ecf216205ccfe72bbdee3183489ad0b67eef0100/requirements.txt https://github.com/qtile/qtile/blob/ecf216205ccfe72bbdee3183... All the heavy lifting is offloaded to C libraries. So, no, you shouldn't see a significant performance penalty, unless your Python WM is doing bitcoin mining in the background or something.