Python ModuleNotFoundError Fix

ModuleNotFoundError usually means the code runs with a different Python interpreter or environment than the one where the package was installed.

Symptoms

  • Import fails even after pip install.
  • The app works locally but fails in cron, Docker or CI.
  • python and pip point to different locations.

Likely causes

  • Wrong virtual environment is active.
  • pip installed into a different interpreter.
  • PYTHONPATH or package layout is incorrect.

Fix steps

  1. Run python -m pip show package-name.
  2. Check which python and python --version in the failing environment.
  3. Activate the correct virtualenv or install inside the container/CI environment.

Verify the fix

  • Run python -c "import package" with the same interpreter.
  • Check cron, systemd or Docker command paths.
  • Add dependencies to requirements or pyproject files.

FAQ

Why does pip say installed but import fails?

pip may belong to a different Python interpreter. Use python -m pip.

Can Docker use my local virtualenv?

No. Install dependencies inside the image or container environment.

Related tools and guides

Docker Docker Compose Generator

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 Cron Cron Expression Explainer

Explain common five-field cron expressions and catch basic schedule mistakes before adding a job to production.

 Docker Docker Compose and .env Workflow for Local Development

Local stacks are easier to maintain when docker-compose.yml describes services and .env.example documents configuration without real secrets.

Last updated: May 18, 2026