Python importing wrong version — virtual environment confusion

Python imports the wrong version of a package, or pip install succeeds but import fails. The installed package version does not match what Python sees at runtime.

The active Python interpreter and pip may point to different environments. Check: (1) which python3 and which pip3 — are they in the same venv? (2) python3 -c 'import sys; print(sys.executable)' — confirms actual interpreter. (3) pip3 install shows 'Requirement already satisfied' but in wrong location. Fix: always use python3 -m pip install to ensure pip matches the active interpreter. Use python3 -m venv consistently. Check sys.path for unexpected entries.

System Python, Homebrew Python, conda, and venvs can coexist. PATH order determines which python/pip runs. pip installed in one environment is invisible to another.