actions/setup-python caching for setup.py projects#

I used to use a combination of actions/setup-python and actions/cache in all of my Python GitHub Actions projects in order to install Python dependencies via a cache, rather than hitting PyPI to download copies every time.

actions/setup-python added built-in caching a while ago, but it wasn’t obvious to me from the documentation how I could use that with setup.py based projects (as opposed to projects that install dependencies via Pipfile or requirements.txt).

The trick is to use cache: pip and cache-dependency-path: setup.py as arguments to the actions/setup-python action.

Here’s the pattern I found that works:

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    - name: Set up Python 3.11
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      uses: actions/setup-python@v4
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      with:
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        python-version: '3.11'
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        cache: pip
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        cache-dependency-path: setup.py
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    - name: Install dependencies
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      run: |
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        pip install '.[test]'

And here’s a full .github/workflows/test.yml configuration that uses a matrix to run tests against five currently supported Python versions:

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name: Test
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on: [push, pull_request]
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permissions:
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  contents: read
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jobs:
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  test:
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    runs-on: ubuntu-latest
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    strategy:
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      matrix:
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        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
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    steps:
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    - uses: actions/checkout@v3
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    - name: Set up Python ${{ matrix.python-version }}
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      uses: actions/setup-python@v4
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      with:
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        python-version: ${{ matrix.python-version }}
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        cache: pip
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        cache-dependency-path: setup.py
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    - name: Install dependencies
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      run: |
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        pip install '.[test]'
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    - name: Run tests
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      run: |
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        pytest

I updated my various cookiecutter templates to use this new pattern in this issue.