How to Cache pip and Poetry Dependencies in CI

Reinstalling Python packages on every run is wasted time. Cache the wheels and the virtualenv and installs drop to seconds.

setup-python can cache pip and Poetry downloads out of the box. For full speed, also cache the resolved virtualenv.

pip: built-in cache

setup-python caches the pip download cache keyed on your requirements file.

- uses: actions/setup-python@v5
  with:
    python-version: '3.12'
    cache: pip
- run: pip install -r requirements.txt

Poetry: cache the virtualenv

Point Poetry at an in-project venv and cache it keyed on poetry.lock for the fastest installs.

- uses: actions/setup-python@v5
  with:
    python-version: '3.12'
    cache: poetry
- run: poetry install --no-interaction

Key on the lockfile

Cache keys should hash requirements.txt or poetry.lock so a dependency bump invalidates cleanly and you never run on stale packages.

Key takeaways

• setup-python cache=pip / cache=poetry covers most cases.
• Cache the virtualenv for the fastest Poetry installs.
• Key caches on the lockfile so bumps invalidate correctly.

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