CI/CD Pipelines

CI/CD for Python services runs ruff, pytest, image build, and staged deploy on every merge. Pipelines enforce the same commands developers run locally with uv and pin Python 3.14.0 in CI matrices.

Recipe

# .github/workflows/ci.yml (excerpt)
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v5
      - run: uv sync --frozen
      - run: uv run ruff check .
      - run: uv run pytest -q

When to reach for this:

Every team merge to main should be deploy-candidate quality
Docker image build after tests pass
Promotion dev → staging → prod with approvals
GitOps tag bump triggers cluster rollout

Working Example

GitHub Actions: test, build/push image, deploy staging with OIDC to AWS.

name: ci-cd
on:
  push:
    branches: [main]
 
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v5
        with:
          python-version: "3.14"
      - run: uv sync --frozen
      - run: uv run ruff check .
      - run: uv run pytest -q --cov=app
 
  build:
    needs: test
    runs-on: ubuntu-latest
    permissions:
      id-token: write
      contents: read
    steps:
      - uses: actions/checkout@v4
      - uses: aws-actions/configure-aws-credentials@v4
        with:
          role-to-assume: arn:aws:iam::123456789012:role/ci-ecr-push
          aws-region: us-east-1
      - uses: docker/build-push-action@v6
        with:
          push: true
          tags: 123456789012.dkr.ecr.us-east-1.amazonaws.com/api:${{ github.sha }}
 
  deploy-staging:
    needs: build
    runs-on: ubuntu-latest
    environment: staging
    steps:
      - run: echo "kubectl set image deployment/api api=...:${{ github.sha }}"

What this demonstrates:

uv sync --frozen matches lockfile in CI
OIDC role assumption avoids static AWS keys
Image tagged with github.sha for traceability
Deploy job gated on environment: staging approval rules

Deep Dive

Pipeline Stages

Stage	Gates
Lint/test	ruff, mypy optional, pytest
Build	Dockerfile, scan image
Deploy dev	auto on main
Deploy prod	manual approval + smoke test

Local/CI Parity

uv run ruff check . && uv run pytest -q
docker build -t api:local .

Python Notes

- run: uv run python -m build   # library packages
- run: uv publish               # PyPI when releasing libs not services

Gotchas

CI uses different Python than prod - subtle bugs. Fix: pin 3.14 in workflow and Docker image.
Skipping tests on docs-only changes - path filters can miss coupled code. Fix: conservative triggers or monorepo rules.
:latest deploy tag - rollback impossible. Fix: immutable SHA tags only.
Secrets in workflow YAML - use GitHub Environments secrets and OIDC.
No smoke test post-deploy - broken health endpoint in prod. Fix: curl /health step after deploy.

Alternatives

Alternative	Use When	Don't Use When
GitLab CI	GitLab hosting	GitHub-only org
Buildkite	Self-hosted agents	Simple GitHub Actions enough
ArgoCD GitOps	K8s deploy drift detection	Single VM docker compose

FAQs

What must run in prebuild?

This repo runs lint-docs in prebuild - keep docs valid when shipping content with code.

uv vs pip in CI?

uv faster and lockfile-native - align with manifest uv 0.6+ pin.

How do I cache deps?

setup-uv with cache enabled or Docker buildkit cache mounts for uv sync layer.

Database migrations in CD?

Separate job before traffic shift - never only in app startup without coordination.

How do I promote staging to prod?

Retag tested SHA or replay deploy job with prod environment approval - same artifact, no rebuild.

Feature flags vs branches?

Trunk-based with flags preferred; long-lived env branches rot.

How do I run integration tests?

pytest marker with docker-compose service deps in CI job or ephemeral preview env.

Monorepo paths?

paths: filters per package - but run smoke whole-system tests on shared lib changes.

How does ruff 0.9+ fit?

Single tool for lint+format - fast CI step before pytest.

Rollback strategy?

Redeploy previous image tag - document in Runbook linked from Deployment Best Practices.

Dockerizing Python - image build
Testing Infrastructure Code - CI policy patterns
Zero-Downtime Deploys - rollout safety
pytest Setup - test layout
Deployment Best Practices - pipeline checklist

Stack versions: This page was written for Python 3.14.0 (stable 3.14, maintenance 3.13), FastAPI 0.115+, Django 5.2, Flask 3.1, Pydantic 2, PyTorch 2.6+, pandas 2.2+, Polars 1.x, ruff 0.9+, and uv 0.6+.

CI/CD Pipelines

Recipe

# .github/workflows/ci.yml (excerpt)
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v5
      - run: uv sync --frozen
      - run: uv run ruff check .
      - run: uv run pytest -q

When to reach for this:

Every team merge to main should be deploy-candidate quality
Docker image build after tests pass
Promotion dev → staging → prod with approvals
GitOps tag bump triggers cluster rollout

Working Example

GitHub Actions: test, build/push image, deploy staging with OIDC to AWS.

name: ci-cd
on:
  push:
    branches: [main]
 
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: astral-sh/setup-uv@v5
        with:
          python-version: "3.14"
      - run: uv sync --frozen
      - run: uv run ruff check .
      - run: uv run pytest -q --cov=app
 
  build:
    needs: test
    runs-on: ubuntu-latest
    permissions:
      id-token: write
      contents: read
    steps:
      - uses: actions/checkout@v4
      - uses: aws-actions/configure-aws-credentials@v4
        with:
          role-to-assume: arn:aws:iam::123456789012:role/ci-ecr-push
          aws-region: us-east-1
      - uses: docker/build-push-action@v6
        with:
          push: true
          tags: 123456789012.dkr.ecr.us-east-1.amazonaws.com/api:${{ github.sha }}
 
  deploy-staging:
    needs: build
    runs-on: ubuntu-latest
    environment: staging
    steps:
      - run: echo "kubectl set image deployment/api api=...:${{ github.sha }}"

What this demonstrates:

uv sync --frozen matches lockfile in CI
OIDC role assumption avoids static AWS keys
Image tagged with github.sha for traceability
Deploy job gated on environment: staging approval rules

Deep Dive

Pipeline Stages

Stage	Gates
Lint/test	ruff, mypy optional, pytest
Build	Dockerfile, scan image
Deploy dev	auto on main
Deploy prod	manual approval + smoke test

Local/CI Parity

uv run ruff check . && uv run pytest -q
docker build -t api:local .

Python Notes

- run: uv run python -m build   # library packages
- run: uv publish               # PyPI when releasing libs not services

Gotchas

CI uses different Python than prod - subtle bugs. Fix: pin 3.14 in workflow and Docker image.
Skipping tests on docs-only changes - path filters can miss coupled code. Fix: conservative triggers or monorepo rules.
:latest deploy tag - rollback impossible. Fix: immutable SHA tags only.
Secrets in workflow YAML - use GitHub Environments secrets and OIDC.
No smoke test post-deploy - broken health endpoint in prod. Fix: curl /health step after deploy.

Alternatives

Alternative	Use When	Don't Use When
GitLab CI	GitLab hosting	GitHub-only org
Buildkite	Self-hosted agents	Simple GitHub Actions enough
ArgoCD GitOps	K8s deploy drift detection	Single VM docker compose

FAQs

What must run in prebuild?

This repo runs lint-docs in prebuild - keep docs valid when shipping content with code.

uv vs pip in CI?

uv faster and lockfile-native - align with manifest uv 0.6+ pin.

How do I cache deps?

setup-uv with cache enabled or Docker buildkit cache mounts for uv sync layer.

Database migrations in CD?

Separate job before traffic shift - never only in app startup without coordination.

How do I promote staging to prod?

Retag tested SHA or replay deploy job with prod environment approval - same artifact, no rebuild.

Feature flags vs branches?

Trunk-based with flags preferred; long-lived env branches rot.

How do I run integration tests?

pytest marker with docker-compose service deps in CI job or ephemeral preview env.

Monorepo paths?

paths: filters per package - but run smoke whole-system tests on shared lib changes.

How does ruff 0.9+ fit?

Single tool for lint+format - fast CI step before pytest.

Rollback strategy?

Redeploy previous image tag - document in Runbook linked from Deployment Best Practices.

Dockerizing Python - image build
Testing Infrastructure Code - CI policy patterns
Zero-Downtime Deploys - rollout safety
pytest Setup - test layout
Deployment Best Practices - pipeline checklist

Stack versions: This page was written for Python 3.14.0 (stable 3.14, maintenance 3.13), FastAPI 0.115+, Django 5.2, Flask 3.1, Pydantic 2, PyTorch 2.6+, pandas 2.2+, Polars 1.x, ruff 0.9+, and uv 0.6+.

CI/CD Pipelines

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CI/CD Pipelines