If you just want a list of the occurences of “TODO” in .py files in the working directory, you can just use :vimgrep like so:
:vimgrep TODO **/*.py
Then open the quickfix window with:
:cw
(it might open it automatically anyway, not sure) and just scroll through the results, hitting Enter to go to each occurrence.
For more complicated management, I’d probably recommend setting up an issue tracker.