setup-python/README.md

# setup-python V2

<p align="left">
  <a href="https://github.com/actions/setup-python"><img alt="GitHub Actions status" src="https://github.com/actions/setup-python/workflows/Main%20workflow/badge.svg"></a>
</p>

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](https://github.com/actions/python-versions/releases)) 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 and pipenv.
- registering problem matchers for error output.

# What's new

- 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 and pipenv dependencies

# Usage

See [action.yml](action.yml)

Basic:
```yaml
steps:
- uses: actions/checkout@v2
- uses: actions/setup-python@v2
  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:
```yaml
jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version: [ '2.x', '3.x', 'pypy-2.7', 'pypy-3.7', 'pypy-3.8' ]
    name: Python ${{ matrix.python-version }} sample
    steps:
      - uses: actions/checkout@v2
      - name: Set up Python
        uses: actions/setup-python@v2
        with:
          python-version: ${{ matrix.python-version }}
          architecture: x64
      - run: python my_script.py
```

Exclude a specific Python version:
```yaml
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', 'pypy-2.7', 'pypy-3.8']
        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@v2
        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:
```yaml
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@v2
    - uses: actions/setup-python@v2
      with:
        python-version: ${{ matrix.python-version }}
    - run: python my_script.py
```

Download and set up an accurate pre-release version of Python:
```yaml
steps:
- uses: actions/checkout@v2
- uses: actions/setup-python@v2
  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):
```yaml
steps:
- uses: actions/checkout@v2
- uses: actions/setup-python@v2
  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:

```yaml
jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version:
        - 'pypy-3.7' # the latest available version of PyPy that supports Python 3.7
        - 'pypy-3.7-v7.3.3' # Python 3.7 and PyPy 7.3.3
        - 'pypy-3.8' # the latest available version of PyPy that supports Python 3.8
    steps:
    - uses: actions/checkout@v2
    - uses: actions/setup-python@v2
      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](#available-versions-of-pypy) section.

# Getting started with Python + Actions

Check out our detailed guide on using [Python with GitHub Actions](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/using-python-with-github-actions).

# Available versions of Python

`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](https://docs.github.com/en/actions/reference/specifications-for-github-hosted-runners#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.
- Downloadable Python versions from GitHub Releases ([actions/python-versions](https://github.com/actions/python-versions/releases)).
    - All available versions are listed in the [version-manifest.json](https://github.com/actions/python-versions/blob/main/versions-manifest.json) file.
    - If there is a specific version of Python that is not available, you can open an issue here

 # Available versions of PyPy

 `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](https://docs.github.com/en/actions/reference/specifications-for-github-hosted-runners#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 `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 `pypy-3.7-v7.3.3`.

- Downloadable PyPy versions from the [official PyPy site](https://downloads.python.org/pypy/).
  - All available versions that we can download are listed in [versions.json](https://downloads.python.org/pypy/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/

# Hosted Tool Cache

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.

|| Location |
|------|-------|
|**Tool Cache Directory** |`RUNNER_TOOL_CACHE`|
|**Python Tool Cache**|`RUNNER_TOOL_CACHE/Python/*`|
|**PyPy Tool Cache**|`RUNNER_TOOL_CACHE/PyPy/*`|

GitHub virtual environments are setup in [actions/virtual-environments](https://github.com/actions/virtual-environments). During the setup, the available versions of Python and PyPy are automatically downloaded, setup and documented.
- [Tools cache setup for Ubuntu](https://github.com/actions/virtual-environments/blob/main/images/linux/scripts/installers/hosted-tool-cache.sh)
- [Tools cache setup for Windows](https://github.com/actions/virtual-environments/blob/main/images/win/scripts/Installers/Download-ToolCache.ps1)

# Specifying a Python version

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.

# Specifying a PyPy version
The version of PyPy should be specified in the format `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.

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

# Caching packages dependencies

The action has built-in functionality for caching and restoring dependencies. It uses [actions/cache](https://github.com/actions/toolkit/tree/main/packages/cache) under the hood for caching dependencies but requires less configuration settings. Supported package managers are `pip` and `pipenv`. 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 or `Pipfile.lock` for pipenv) 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

**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:**  

```yaml
steps:
- uses: actions/checkout@v2
- uses: actions/setup-python@v2
  with:
    python-version: '3.9'
    cache: 'pip'
- run: pip install -r requirements.txt
```

**Caching pipenv dependencies:**
```yaml
steps:
- uses: actions/checkout@v2
- name: Install pipenv
  run: pipx install pipenv
- uses: actions/setup-python@v2
  with:
    python-version: '3.9'
    cache: 'pipenv'
- run: pipenv install
```

**Using wildcard patterns to cache dependencies**
```yaml
steps:
- uses: actions/checkout@v2
- uses: actions/setup-python@v2
  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**
```yaml
steps:
- uses: actions/checkout@v2
- name: Install pipenv
  run: pipx install pipenv
- uses: actions/setup-python@v2
  with:
    python-version: '3.9'
    cache: 'pipenv'
    cache-dependency-path: |
      server/app/Pipfile.lock
      __test__/app/Pipfile.lock      
- run: pipenv install
```

# Using `setup-python` with a self hosted runner

Python distributions are only available for the same [environments](https://github.com/actions/virtual-environments#available-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](https://github.com/actions/toolkit/blob/main/docs/action-debugging.md#step-debug-logs) to see addition logs.

### Windows

- 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.

### Linux

- The Python packages that are downloaded from `actions/python-versions` are originally compiled from source in `/opt/hostedtoolcache/` with the [--enable-shared](https://github.com/actions/python-versions/blob/94f04ae6806c6633c82db94c6406a16e17decd5c/builders/ubuntu-python-builder.psm1#L35) 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](https://help.github.com/en/actions/hosting-your-own-runners/configuring-the-self-hosted-runner-application-as-a-service#checking-the-status-of-the-service).

### Mac

- 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.


# Using Python without `setup-python`

`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`.

# Using `setup-python` on GHES

`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`](https://github.com/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](https://docs.github.com/en/rest/overview/resources-in-the-rest-api#rate-limiting). 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](https://docs.github.com/en/enterprise-server@2.22/admin/github-actions/managing-access-to-actions-from-githubcom/setting-up-the-tool-cache-on-self-hosted-runners-without-internet-access#about-the-included-setup-actions-and-the-runner-tool-cache).

# License

The scripts and documentation in this project are released under the [MIT License](LICENSE).

# Contributions

Contributions are welcome! See our [Contributor's Guide](docs/contributors.md).