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

• optionally installing and adding to PATH a version of Python that is already installed in the tools cache.
• downloading, installing and adding to PATH an available version of Python from GitHub Releases (actions/python-versions) if a specific version is not available in the tools cache.
• failing if a specific version of Python is not preinstalled or available for download.
• optionally caching dependencies for pip, pipenv and poetry.
• registering problem matchers for error output.

• Ability to download, install and set up Python packages from actions/python-versions that do not come preinstalled on runners.
  • Allows for pinning to a specific patch version of Python without the worry of it ever being removed or changed.
• Automatic setup and download of Python packages if using a self-hosted runner.
• Support for pre-release versions of Python.
• Support for installing any version of PyPy on-flight
• Support for built-in caching of pip, pipenv and poetry dependencies

See action.yml

Basic:

steps:
- uses: actions/checkout@v3
- uses: actions/setup-python@v3
  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', 'pypy2.7', 'pypy3.7', 'pypy3.8' ]
    name: Python ${{ matrix.python-version }} sample
    steps:
      - uses: actions/checkout@v3
      - name: Set up Python
        uses: actions/setup-python@v3
        with:
          python-version: ${{ matrix.python-version }}
          architecture: x64
      - run: python my_script.py

Exclude a specific Python version:

jobs:
  build:
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
        python-version: ['2.7', '3.7', '3.8', '3.9', '3.10', 'pypy2.7', 'pypy3.8']
        exclude:
          - os: macos-latest
            python-version: '3.8'
          - os: windows-latest
            python-version: '3.6'
    steps:
      - uses: actions/checkout@v3
      - name: Set up Python
        uses: actions/setup-python@v3
        with:
          python-version: ${{ matrix.python-version }}
      - name: Display Python version
        run: python --version

Download and set up a version of Python that does not come preinstalled on an image:

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        # in this example, there is a newer version already installed, 3.7.7, so the older version will be downloaded
        python-version: ['3.7.4', '3.8', '3.9', '3.10']
    steps:
    - uses: actions/checkout@v3
    - uses: actions/setup-python@v3
      with:
        python-version: ${{ matrix.python-version }}
    - run: python my_script.py

Download and set up an accurate pre-release version of Python:

steps:
- uses: actions/checkout@v3
- uses: actions/setup-python@v3
  with:
    python-version: '3.11.0-alpha.1'
- run: python my_script.py

Download and set up the latest available version of Python (includes both pre-release and stable versions):

steps:
- uses: actions/checkout@v3
- uses: actions/setup-python@v3
  with:
    python-version: '3.11.0-alpha - 3.11.0' # SemVer's version range syntax
- run: python my_script.py

Download and set up PyPy:

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version:
        - 'pypy3.7' # the latest available version of PyPy that supports Python 3.7
        - 'pypy3.7-v7.3.3' # Python 3.7 and PyPy 7.3.3
        - 'pypy3.8' # the latest available version of PyPy that supports Python 3.8
    steps:
    - uses: actions/checkout@v3
    - uses: actions/setup-python@v3
      with:
        python-version: ${{ matrix.python-version }}
    - run: python my_script.py

More details on PyPy syntax and examples of using preview / nightly versions of PyPy can be found in the Available versions of PyPy section.

An output is available with the absolute path of the python interpreter executable if you need it:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v3
    - uses: actions/setup-python@v3
      id: cp310
      with:
        python-version: "3.10"
    - run: pipx run --python '${{ steps.cp310.outputs.python-path }}' nox --version

The environment variable pythonLocation also becomes available after Python or PyPy installation. It contains the absolute path to the folder where the desired version of Python or PyPy is installed.

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

setup-python is able to configure Python from two sources:

• Preinstalled versions of Python in the tools cache on GitHub-hosted runners.
  • For detailed information regarding the available versions of Python that are installed, see Supported software.
  • For every minor version of Python, expect only the latest patch to be preinstalled.
  • If 3.8.1 is installed for example, and 3.8.2 is released, expect 3.8.1 to be removed and replaced by 3.8.2 in the tools cache.
  • If the exact patch version doesn't matter to you, specifying just the major and minor version will get you the latest preinstalled patch version. In the previous example, the version spec 3.8 will use the 3.8.2 Python version found in the cache.
  • Use -dev instead of a patch number (e.g., 3.11-dev) to install the latest patch version release for a given minor version, alpha and beta releases included.
• Downloadable Python versions from GitHub Releases (actions/python-versions).
  • All available versions are listed in the version-manifest.json file.
  • If there is a specific version of Python that is not available, you can open an issue here

Note: Python versions used in this action are generated in the python-versions repository. For macOS and Ubuntu images python versions are built from the source code. For Windows the python-versions repository uses installation executable. For more information please refer to the python-versions repository.

setup-python is able to configure PyPy from two sources:

• Preinstalled versions of PyPy in the tools cache on GitHub-hosted runners

  • For detailed information regarding the available versions of PyPy that are installed, see Supported software.
  • For the latest PyPy release, all versions of Python are cached.
  • Cache is updated with a 1-2 week delay. If you specify the PyPy version as pypy3.7 or pypy-3.7, the cached version will be used although a newer version is available. If you need to start using the recently released version right after release, you should specify the exact PyPy version using pypy3.7-v7.3.3 or pypy-3.7-v7.3.3.

• Downloadable PyPy versions from the official PyPy site.

  • All available versions that we can download are listed in versions.json file.
  • PyPy < 7.3.3 are not available to install on-flight.
  • If some versions are not available, you can open an issue in https://foss.heptapod.net/pypy/pypy/

GitHub hosted runners have a tools cache that comes with a few versions of 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: Install-Toolset.ps1 Configure-Toolset.ps1
• Tools cache setup for Windows: Install-Toolset.ps1 Configure-Toolset.ps1

If there is a specific version of Python that you need and you don't want to worry about any potential breaking changes due to patch updates (going from 3.7.5 to 3.7.6 for example), you should specify the exact major, minor, and patch version (such as 3.7.5)

• The only downside to this is that set up will take a little longer since the exact version will have to be downloaded if the exact version is not already installed on the runner due to more recent versions.
• MSI installers are used on Windows for this, so runs will take a little longer to set up vs Mac and Linux.

You should specify only a major and minor version if you are okay with the most recent patch version being used.

• There will be a single patch version already installed on each runner for every minor version of Python that is supported.
• The patch version that will be preinstalled, will generally be the latest and every time there is a new patch released, the older version that is preinstalled will be replaced.
• Using the most recent patch version will result in a very quick setup since no downloads will be required since a locally installed version Python on the runner will be used.

The version of PyPy should be specified in the format pypy<python_version>[-v<pypy_version>] or pypy-<python_version>[-v<pypy_version>]. The <pypy_version> parameter is optional and can be skipped. The latest version will be used in this case.

pypy3.7 or pypy-3.7 # the latest available version of PyPy that supports Python 3.7
pypy3.8 or pypy-3.8 # the latest available version of PyPy that supports Python 3.8
pypy2.7 or pypy-2.7 # the latest available version of PyPy that supports Python 2.7
pypy3.7-v7.3.3 or pypy-3.7-v7.3.3 # Python 3.7 and PyPy 7.3.3
pypy3.7-v7.x or pypy-3.7-v7.x # Python 3.7 and the latest available PyPy 7.x
pypy3.7-v7.3.3rc1 or pypy-3.7-v7.3.3rc1 # Python 3.7 and preview version of PyPy
pypy3.7-nightly or pypy-3.7-nightly # Python 3.7 and nightly PyPy

The action has built-in functionality for caching and restoring dependencies. It uses actions/cache under the hood for caching dependencies but requires less configuration settings. Supported package managers are pip, pipenv and poetry. The cache input is optional, and caching is turned off by default.

The action defaults to searching for a dependency file (requirements.txt for pip, Pipfile.lock for pipenv or poetry.lock for poetry) in the repository, and uses its hash as a part of the cache key. Use cache-dependency-path for cases where multiple dependency files are used, they are located in different subdirectories or different files for the hash want to be used.

• For pip, the action will cache global cache directory
• For pipenv, the action will cache virtualenv directory
• For poetry, the action will cache virtualenv directory

Please Note: Restored cache will not be used if the requirements.txt file is not updated for a long time and a newer version of the dependency is available that can lead to an increase in total build time.

The requirements file format allows to specify dependency versions using logical operators (for example chardet>=3.0.4) or specify dependencies without any versions. In this case the pip install -r requirements.txt command will always try to install the latest available package version. To be sure that the cache will be used, please stick to a specific dependency version and update it manually if necessary.

Caching pip dependencies:

steps:
- uses: actions/checkout@v3
- uses: actions/setup-python@v3
  with:
    python-version: '3.9'
    cache: 'pip'
- run: pip install -r requirements.txt

Caching pipenv dependencies:

steps:
- uses: actions/checkout@v3
- name: Install pipenv
  run: pipx install pipenv
- uses: actions/setup-python@v3
  with:
    python-version: '3.9'
    cache: 'pipenv'
- run: pipenv install

Caching poetry dependencies:

steps:
- uses: actions/checkout@v3
- name: Install poetry
  run: pipx install poetry
- uses: actions/setup-python@v3
  with:
    python-version: '3.9'
    cache: 'poetry'
- run: poetry install
- run: poetry run pytest

Using wildcard patterns to cache dependencies

steps:
- uses: actions/checkout@v3
- uses: actions/setup-python@v3
  with:
    python-version: '3.9'
    cache: 'pip'
    cache-dependency-path: '**/requirements-dev.txt'
- run: pip install -r subdirectory/requirements-dev.txt

Using a list of file paths to cache dependencies

steps:
- uses: actions/checkout@v3
- name: Install pipenv
  run: pipx install pipenv
- uses: actions/setup-python@v3
  with:
    python-version: '3.9'
    cache: 'pipenv'
    cache-dependency-path: |
      server/app/Pipfile.lock
      __test__/app/Pipfile.lock
- run: pipenv install

Python distributions are only available for the same environments that GitHub Actions hosted environments are available for. If you are using an unsupported version of Ubuntu such as 19.04 or another Linux distribution such as Fedora, setup-python will not work. If you have a supported self-hosted runner and you would like to use setup-python, there are a few extra things you need to make sure are set up so that new versions of Python can be downloaded and configured on your runner.

If you are experiencing problems while configuring Python on your self-hosted runner, turn on step debugging to see addition logs.

• Your runner needs to be running with administrator privileges so that the appropriate directories and files can be set up when downloading and installing a new version of Python for the first time.
• If your runner is configured as a service, make sure the account that is running the service has the appropriate write permissions so that Python can get installed. The default NT AUTHORITY\NETWORK SERVICE should be sufficient.
• You need 7zip installed and added to your PATH so that the downloaded versions of Python files can be extracted properly during first-time setup.
• MSI installers are used when setting up Python on Windows. A word of caution as MSI installers update registry settings.
• The 3.8 MSI installer for Windows will not let you install another 3.8 version of Python. If setup-python fails for a 3.8 version of Python, make sure any previously installed versions are removed by going to "Apps & Features" in the Settings app.

• The Python packages that are downloaded from actions/python-versions are originally compiled from source in /opt/hostedtoolcache/ with the --enable-shared flag, which makes them non-relocatable.
• Create an environment variable called AGENT_TOOLSDIRECTORY and set it to /opt/hostedtoolcache. This controls where the runner downloads and installs tools.
  • In the same shell that your runner is using, type export AGENT_TOOLSDIRECTORY=/opt/hostedtoolcache.
  • A more permanent way of setting the environment variable is to create a .env file in the same directory as your runner and to add AGENT_TOOLSDIRECTORY=/opt/hostedtoolcache. This ensures the variable is always set if your runner is configured as a service.
• Create a directory called hostedtoolcache inside /opt.
• The user starting the runner must have write permission to the /opt/hostedtoolcache directory. It is not possible to start the Linux runner with sudo and the /opt directory usually requires root privileges to write to. Check the current user and group that the runner belongs to by typing ls -l inside the runners root directory.
• The runner can be granted write access to the /opt/hostedtoolcache directory using a few techniques:
  • The user starting the runner is the owner, and the owner has write permission.
  • The user starting the runner is in the owning group, and the owning group has write permission.
  • All users have write permission.
• One quick way to grant access is to change the user and group of /opt/hostedtoolcache to be the same as the runners using chown.
  • sudo chown runner-user:runner-group /opt/hostedtoolcache/.
• If your runner is configured as a service and you run into problems, make sure the user that the service is running as is correct. For more information, you can check the status of your self-hosted runner.

• The same setup that applies to Linux also applies to Mac, just with a different tools cache directory.
• Create a directory called /Users/runner/hostedtoolcache.
• Set the AGENT_TOOLSDIRECTORY environment variable to /Users/runner/hostedtoolcache.
• Change the permissions of /Users/runner/hostedtoolcache so that the runner has write access.

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.

setup-python comes pre-installed on the appliance with GHES if Actions is enabled. When dynamically downloading Python distributions, setup-python downloads distributions from actions/python-versions on github.com (outside of the appliance). These calls to actions/python-versions are made via unauthenticated requests, which are limited to 60 requests per hour per IP. If more requests are made within the time frame, then you will start to see rate-limit errors during download that read ##[error]API rate limit exceeded for....

To avoid hitting rate-limit problems, we recommend setting up your own runner tool cache.

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

Contributions are welcome! See our Contributor's Guide.