Python CI

~13 min · python, pytest, setup-python

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The default Python pipeline in 2026

The Python ecosystem in 2026 looks different from five years ago. uv (Astral) replaces pip + virtualenv for most workflows. ruff replaces flake8/isort/black. pyright or mypy for types. pytest remains the standard test runner. pyproject.toml centralizes config.

The default Python CI shape:

Checkout.
Install uv (fast, single binary).
uv sync — install deps from pyproject.toml + lockfile.
ruff check + ruff format --check — lint and format gate.
mypy or pyright — type-check.
pytest — run tests with coverage.

Pinning matters more than convenience

Always pin Python: python-version: '3.12', not '3.x' or blank. Pin uv too: astral-sh/setup-uv@v3 with a specific version. CI that drifts when an underlying tool ships a new release is CI you cannot trust on a Friday afternoon.

Code

Python CI with uv (2026 standard)·yaml

name: ci
on: { pull_request: {}, push: { branches: [main] } }
permissions: read-all
concurrency: { group: ci-${{ github.ref }}, cancel-in-progress: true }

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v3
        with:
          version: '0.5.x'
          enable-cache: true
      - name: Install Python
        run: uv python install 3.12
      - name: Sync deps
        run: uv sync --all-extras --dev
      - name: Lint
        run: uv run ruff check .
      - name: Format check
        run: uv run ruff format --check .
      - name: Type check
        run: uv run mypy src
      - name: Test
        run: uv run pytest -q --cov=src --cov-report=xml

External links

Exercise

If your project still uses pip in CI, swap it for uv. Time both before and after the migration. The difference on a project with ~50 deps is usually 30–60 seconds per run.