Setup

Use a single Python version

Specify 3.x for the latest version, or 3.8 for example to target a version.

• build.yml

    name: Python package
  
    on: push
  
    jobs:
      build:
        runs-on: ubuntu-latest
  
        steps:
        - uses: actions/checkout@v2
  
        - name: Set up Python 3.x
          uses: actions/setup-python@v2
          with:
            python-version: '3.x'
  

Use a matrix

• build.yml

    name: Python package
  
    on: push
  
    jobs:
      build:
        runs-on: ubuntu-latest
  
        strategy:
          matrix:
            max-parallel: 4
            python-version: [2.7, 3.5, 3.6, 3.7, 3.8]
  
        steps:
          - uses: actions/checkout@v2
  
          - name: Set up Python $
            uses: actions/setup-python@v2
            with:
              python-version: $
  

Alternately use just two versions:

strategy:
  matrix:
    python-version: [3.6, 3.X]

You can test your matrix by printing the current Python version

- name: Display Python version
  run: python -c "import sys; print(sys.version)"

Or simply python -V.