Quick Reference

Action	Purpose	Speed
astral-sh/setup-uv@v4	Install uv + caching	10-100x faster
actions/setup-python@v5	Traditional pip	Baseline

uv CI Pattern	Code
Setup	uses: astral-sh/setup-uv@v4 with enable-cache: true
Install Python	uv python install ${{ matrix.python-version }}
Sync deps	uv sync --all-extras
Run tests	uv run pytest

Matrix Strategy	Config
Python versions	python-version: ["3.11", "3.12", "3.13"]
Operating systems	os: [ubuntu-latest, windows-latest, macos-latest]
Fail fast	fail-fast: false for full coverage

Optimization	Technique
Caching	enable-cache: true with setup-uv
Parallel jobs	Split lint/test/build
Concurrency	cancel-in-progress: true
Path filters	paths: ["src/**", "tests/**"]

When to Use This Skill

Use for CI/CD pipelines:

• Setting up GitHub Actions for Python projects
• Caching dependencies for fast builds
• Matrix testing across Python versions
• Publishing packages to PyPI
• Code coverage and security scanning

Related skills:

• For package management: see python-package-management
• For testing: see python-testing
• For type checking: see python-type-hints

---

Python GitHub Actions Optimization

Overview

GitHub Actions is the primary CI/CD platform for Python projects. This guide covers best practices for fast, reliable, and efficient Python workflows.

Quick Start Workflow

# .github/workflows/ci.yml
name: CI

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version: ["3.11", "3.12", "3.13"]

    steps:
      - uses: actions/checkout@v4

      - name: Install uv
        uses: astral-sh/setup-uv@v4

      - name: Set up Python ${{ matrix.python-version }}
        run: uv python install ${{ matrix.python-version }}

      - name: Install dependencies
        run: uv sync --all-extras --dev

      - name: Run linting
        run: uv run ruff check .

      - name: Run type checking
        run: uv run mypy src

      - name: Run tests
        run: uv run pytest --cov

Modern uv-Based Workflow

Setup with uv

name: CI with uv

on:
  push:
    branches: [main]
  pull_request:

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Install uv
        uses: astral-sh/setup-uv@v4
        with:
          version: "latest"
          enable-cache: true  # Automatic caching!

      - name: Lint with ruff
        run: |
          uv run ruff check .
          uv run ruff format --check .

  type-check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - uses: astral-sh/setup-uv@v4
        with:
          enable-cache: true

      - name: Type check with mypy
        run: uv run mypy src

  test:
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        python-version: ["3.11", "3.12", "3.13"]

    steps:
      - uses: actions/checkout@v4

      - uses: astral-sh/setup-uv@v4
        with:
          enable-cache: true

      - name: Set up Python
        run: uv python install ${{ matrix.python-version }}

      - name: Install dependencies
        run: uv sync --all-extras

      - name: Run tests
        run: uv run pytest -v --cov --cov-report=xml

      - name: Upload coverage
        uses: codecov/codecov-action@v4
        with:
          file: ./coverage.xml

Dependency Caching with uv

# uv handles caching automatically with setup-uv
- uses: astral-sh/setup-uv@v4
  with:
    enable-cache: true
    cache-dependency-glob: "uv.lock"

# This caches:
# - Downloaded packages
# - Python installations
# - Virtual environments

Traditional pip-Based Workflow

Manual Caching Setup

name: CI with pip

on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Set up Python
        uses: actions/setup-python@v5
        with:
          python-version: "3.12"
          cache: "pip"  # Built-in pip caching
          cache-dependency-path: |
            requirements.txt
            requirements-dev.txt

      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip
          pip install -r requirements.txt
          pip install -r requirements-dev.txt

      - name: Run tests
        run: pytest

Advanced Caching

- name: Cache pip packages
  uses: actions/cache@v4
  with:
    path: ~/.cache/pip
    key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements*.txt') }}
    restore-keys: |
      ${{ runner.os }}-pip-

- name: Cache pre-commit hooks
  uses: actions/cache@v4
  with:
    path: ~/.cache/pre-commit
    key: pre-commit-${{ hashFiles('.pre-commit-config.yaml') }}

Parallel and Matrix Builds

Efficient Matrix Strategy

jobs:
  test:
    runs-on: ${{ matrix.os }}
    strategy:
      fail-fast: false  # Don't cancel all on first failure
      matrix:
        os: [ubuntu-latest, windows-latest, macos-latest]
        python-version: ["3.11", "3.12", "3.13"]
        exclude:
          # Skip Python 3.13 on Windows (if issues)
          - os: windows-latest
            python-version: "3.13"

    steps:
      - uses: actions/checkout@v4

      - uses: astral-sh/setup-uv@v4
        with:
          enable-cache: true

      - run: uv python install ${{ matrix.python-version }}
      - run: uv sync
      - run: uv run pytest

Split by Test Type

jobs:
  unit:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v4
      - run: uv sync
      - run: uv run pytest tests/unit -v

  integration:
    runs-on: ubuntu-latest
    needs: unit  # Run after unit tests pass
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v4
      - run: uv sync
      - run: uv run pytest tests/integration -v

  e2e:
    runs-on: ubuntu-latest
    needs: integration
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v4
      - run: uv sync
      - run: uv run pytest tests/e2e -v

Reusable Workflows

Composite Action

# .github/actions/python-setup/action.yml
name: Python Setup
description: Set up Python environment with uv

inputs:
  python-version:
    description: Python version to use
    default: "3.12"

runs:
  using: composite
  steps:
    - name: Install uv
      uses: astral-sh/setup-uv@v4
      with:
        enable-cache: true

    - name: Set up Python
      shell: bash
      run: uv python install ${{ inputs.python-version }}

    - name: Install dependencies
      shell: bash
      run: uv sync --all-extras

# .github/workflows/ci.yml
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: ./.github/actions/python-setup
        with:
          python-version: "3.12"
      - run: uv run pytest

Reusable Workflow

# .github/workflows/python-test.yml
name: Reusable Python Test

on:
  workflow_call:
    inputs:
      python-version:
        type: string
        default: "3.12"

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - uses: astral-sh/setup-uv@v4
        with:
          enable-cache: true

      - run: uv python install ${{ inputs.python-version }}
      - run: uv sync
      - run: uv run pytest

# .github/workflows/ci.yml
jobs:
  test-3-11:
    uses: ./.github/workflows/python-test.yml
    with:
      python-version: "3.11"

  test-3-12:
    uses: ./.github/workflows/python-test.yml
    with:
      python-version: "3.12"

YAML Anchors (2025 Feature)

# Reduce repetition with anchors
name: CI

on: [push, pull_request]

# Define anchor
x-common-steps: &common-steps
  - uses: actions/checkout@v4
  - uses: astral-sh/setup-uv@v4
    with:
      enable-cache: true

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      *common-steps  # Reference anchor
      - run: uv run ruff check .

  test:
    runs-on: ubuntu-latest
    steps:
      *common-steps  # Reuse same steps
      - run: uv sync
      - run: uv run pytest

Publishing to PyPI

name: Publish

on:
  release:
    types: [published]

jobs:
  publish:
    runs-on: ubuntu-latest
    permissions:
      id-token: write  # Required for trusted publishing

    steps:
      - uses: actions/checkout@v4

      - uses: astral-sh/setup-uv@v4

      - name: Build package
        run: uv build

      - name: Publish to PyPI
        uses: pypa/gh-action-pypi-publish@release/v1
        # No password needed with trusted publishing!

Comprehensive CI/CD Example

name: CI/CD

on:
  push:
    branches: [main]
  pull_request:
  release:
    types: [published]

env:
  PYTHON_VERSION: "3.12"

jobs:
  # ========== Quality Checks ==========
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v4
        with:
          enable-cache: true
      - run: uv sync --only-dev
      - run: uv run ruff check .
      - run: uv run ruff format --check .

  type-check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v4
        with:
          enable-cache: true
      - run: uv sync
      - run: uv run mypy src

  # ========== Tests ==========
  test:
    needs: [lint, type-check]
    runs-on: ${{ matrix.os }}
    strategy:
      fail-fast: false
      matrix:
        os: [ubuntu-latest, windows-latest, macos-latest]
        python-version: ["3.11", "3.12", "3.13"]

    steps:
      - uses: actions/checkout@v4

      - uses: astral-sh/setup-uv@v4
        with:
          enable-cache: true

      - run: uv python install ${{ matrix.python-version }}
      - run: uv sync

      - name: Run tests
        run: uv run pytest -v --cov --cov-report=xml

      - name: Upload coverage
        if: matrix.os == 'ubuntu-latest' && matrix.python-version == '3.12'
        uses: codecov/codecov-action@v4
        with:
          file: ./coverage.xml
          fail_ci_if_error: true

  # ========== Security ==========
  security:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v4
      - run: uv sync
      - run: uv run pip-audit  # Check for known vulnerabilities
      - run: uv run bandit -r src  # Security linting

  # ========== Build ==========
  build:
    needs: test
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v4

      - name: Build package
        run: uv build

      - name: Upload artifact
        uses: actions/upload-artifact@v4
        with:
          name: dist
          path: dist/

  # ========== Publish ==========
  publish:
    if: github.event_name == 'release'
    needs: build
    runs-on: ubuntu-latest
    permissions:
      id-token: write

    steps:
      - uses: actions/download-artifact@v4
        with:
          name: dist
          path: dist/

      - name: Publish to PyPI
        uses: pypa/gh-action-pypi-publish@release/v1

Performance Optimization Tips

1. Use uv for Fastest Installs

# uv is 10-100x faster than pip
- uses: astral-sh/setup-uv@v4
  with:
    enable-cache: true

2. Fail Fast (or Not)

strategy:
  fail-fast: true   # Cancel all on first failure (faster feedback)
  fail-fast: false  # Run all (complete coverage)

3. Job Dependencies

jobs:
  lint:
    runs-on: ubuntu-latest

  test:
    needs: lint  # Only run if lint passes
    runs-on: ubuntu-latest

4. Concurrency Control

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true  # Cancel previous runs on same branch

5. Skip Unnecessary Runs

on:
  push:
    paths:
      - "src/**"
      - "tests/**"
      - "pyproject.toml"
    paths-ignore:
      - "**.md"
      - "docs/**"

6. ARM64 Runners (2025)

# Free ARM64 runners for public repos
runs-on: ubuntu-24.04-arm64  # Faster for ARM-native workloads

Common Issues & Solutions

Issue: Slow pip install

# Solution: Use uv
- uses: astral-sh/setup-uv@v4
  with:
    enable-cache: true

Issue: Cache not working

# Solution: Verify cache key matches dependency files
- uses: actions/cache@v4
  with:
    path: ~/.cache
    key: deps-${{ hashFiles('uv.lock', 'pyproject.toml') }}

Issue: Python version not found

# Solution: Use uv to manage Python versions
- uses: astral-sh/setup-uv@v4
- run: uv python install 3.13  # Works even for newest versions

Issue: Tests fail on Windows

# Solution: Normalize line endings
- uses: actions/checkout@v4
  with:
    # Prevent Windows line ending issues
    persist-credentials: false

# Or in .gitattributes
# *.py text eol=lf