Comment by Ded7xSEoPKYNsDd

The standard python linters can do it:

    $ flake8 foo.py
    foo.py:6:14: F821 undefined name 'q'

    $ mypy --check-untyped-defs foo.py
    foo.py:6: error: Name 'q' is not defined

(They also have some other complaints about your code that you'd either have to disable or adjust to.)