How to check the root cause of the difference between “pytest” and “python -m pytest”?

Command	Uses which Python?	Risk
pytest	Whatever executable is first in PATH	May run wrong environment
python -m pytest	The Python you explicitly called	Much safer

cat $(which pytest)

The shebang line can show which “python” that pytest uses.

python -c "import sys; print(sys.executable)"

or

which python

This shows the interpreter you’re explicitly invoking.