This action sets up a Python environment for use in actions by:

• optionally installing a version of Python and adding to PATH. Note that this action only uses versions of Python already installed in the cache. The action will fail if no matching versions are found.
• registering problem matchers for error output

See action.yml

Basic:

steps:
- uses: actions/checkout@v2
- uses: actions/setup-python@v1
  with:
    python-version: '3.x' # Version range or exact version of a Python version to use, using SemVer's version range syntax
    architecture: 'x64' # optional x64 or x86. Defaults to x64 if not specified
- run: python my_script.py

Matrix Testing:

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version: [ '2.x', '3.x', 'pypy2', 'pypy3' ]
    name: Python ${{ matrix.python-version }} sample
    steps:
      - uses: actions/checkout@v2
      - name: Setup python
        uses: actions/setup-python@v1
        with:
          python-version: ${{ matrix.python-version }}
          architecture: x64
      - run: python my_script.py

Exclude a specific Python version:

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
        python-version: [2.7, 3.6, 3.7, 3.8, pypy2, pypy3]
        exclude:
          - os: macos-latest
            python-version: 3.8
          - os: windows-latest
            python-version: 3.6
    steps:
      - uses: actions/checkout@v2
      - name: Set up Python
        uses: actions/setup-python@v1
        with:
          python-version: ${{ matrix.python-version }}
      - name: Display Python version
        run: python -c "import sys; print(sys.version)"

Check out our detailed guide on using Python with GitHub Actions.

GitHub hosted runners have a tools cache that comes with Python + PyPy already installed. This tools cache helps speed up runs and tool setup by not requiring any new downloads. There is an environment variable called RUNNER_TOOL_CACHE on each runner that describes the location of this tools cache and there is where you will find Python and PyPy installed. setup-python works by taking a specific version of Python or PyPy in this tools cache and adding it to PATH.

GitHub virtual environments are setup in actions/virtual-environments. During the setup, the available versions of Python and PyPy are automatically downloaded, setup and documented.

• Tools cache setup for Ubuntu
• Tools cache setup for Windows

setup-python helps keep your dependencies explicit and ensures consistent behavior between different runners. If you use python in a shell on a GitHub hosted runner without setup-python it will default to whatever is in PATH. The default version of Python in PATH vary between runners and can change unexpectedly so we recommend you always use setup-python.

For detailed information regarding the available versions of Python that are installed see Software installed on GitHub-hosted runners

The scripts and documentation in this project are released under the MIT License

Contributions are welcome! See Contributor's Guide