Does the package have 5+ internal modules OR multiple contributors OR complex sub-packages?
├── YES → Use src/ layout
│         Reason: prevents accidental import of uninstalled code during development;
│         separates source from project root files; PyPA-recommended for large projects.
│
├── NO → Is it a single-module, focused package (e.g., one file + helpers)?
│         ├── YES → Use flat layout
│         └── NO (medium complexity) → Use flat layout, migrate to src/ if it grows
│
└── Is it multiple related packages under one namespace (e.g., myorg.http, myorg.db)?
          └── YES → Use namespace/monorepo layout

Does the user need version derived automatically from git tags?
├── YES → Use setuptools + setuptools_scm
│         (git tag v1.0.0 → that IS your release workflow)
│
└── NO → Does the user want an all-in-one tool (deps + build + publish)?
          ├── YES → Use poetry (v2+ supports standard [project] table)
          │
          └── NO → Is the package pure Python with no C extensions?
                    ├── YES, minimal config preferred → Use flit
                    │   (zero config, auto-discovers version from __version__)
                    │
                    └── YES, modern & fast preferred → Use hatchling
                        (zero-config, plugin system, no setup.py needed)

Does the package have C/Cython/Fortran extensions?
└── YES → MUST use setuptools (only backend with full native extension support)

1. SOURCE TREE
   Your code in version control (git)
   └── pyproject.toml describes metadata + build system

2. BUILD
   python -m build
   └── Produces two artifacts in dist/:
       ├── *.tar.gz   → source distribution (sdist)
       └── *.whl      → built distribution (wheel) — preferred by pip

3. VALIDATE
   twine check dist/*
   └── Checks metadata, README rendering, and PyPI compatibility

4. TEST PUBLISH (first release only)
   twine upload --repository testpypi dist/*
   └── Verify: pip install --index-url https://test.pypi.org/simple/ your-package

5. PUBLISH
   twine upload dist/*          ← manual fallback
   OR GitHub Actions publish.yml  ← recommended (Trusted Publishing / OIDC)

6. USER INSTALL
   pip install your-package
   pip install "your-package[extra]"

your-package/
├── src/
│   └── your_package/
│       ├── __init__.py           # Public API: __all__, __version__
│       ├── py.typed              # PEP 561 marker — EMPTY FILE
│       ├── core.py               # Primary implementation
│       ├── client.py             # (API client type) or remove
│       ├── cli.py                # (CLI type) click/typer commands, or remove
│       ├── config.py             # Settings / configuration dataclass
│       ├── exceptions.py         # Custom exception hierarchy
│       ├── models.py             # Data classes, Pydantic models, TypedDicts
│       ├── utils.py              # Internal helpers (prefix _utils if private)
│       ├── types.py              # Shared type aliases and TypeVars
│       └── backends/             # (Plugin pattern) — remove if not needed
│           ├── __init__.py       # Protocol / ABC interface definition
│           ├── memory.py         # Default zero-dep implementation
│           └── redis.py          # Optional heavy implementation
├── tests/
│   ├── __init__.py
│   ├── conftest.py               # Shared fixtures
│   ├── unit/
│   │   ├── __init__.py
│   │   ├── test_core.py
│   │   ├── test_config.py
│   │   └── test_models.py
│   ├── integration/
│   │   ├── __init__.py
│   │   └── test_backends.py
│   └── e2e/                      # Optional: end-to-end tests
│       └── __init__.py
├── docs/                         # Optional: mkdocs or sphinx
├── scripts/
│   └── scaffold.py
├── .github/
│   ├── workflows/
│   │   ├── ci.yml
│   │   └── publish.yml
│   └── ISSUE_TEMPLATE/
│       ├── bug_report.md
│       └── feature_request.md
├── .pre-commit-config.yaml
├── pyproject.toml
├── CHANGELOG.md
├── CONTRIBUTING.md
├── SECURITY.md
├── LICENSE
├── README.md
└── .gitignore

your-package/
├── your_package/         # ← at root, not inside src/
│   ├── __init__.py
│   ├── py.typed
│   └── ... (same internal structure)
├── tests/
└── ... (same top-level files)

your-org/
├── packages/
│   ├── your-org-core/
│   │   ├── src/your_org/core/
│   │   └── pyproject.toml
│   ├── your-org-http/
│   │   ├── src/your_org/http/
│   │   └── pyproject.toml
│   └── your-org-cli/
│       ├── src/your_org/cli/
│       └── pyproject.toml
├── .github/workflows/
└── README.md

Canonical form:  N[.N]+[{a|b|rc}N][.postN][.devN]

Examples:
  1.0.0          Stable release
  1.0.0a1        Alpha (pre-release)
  1.0.0b2        Beta
  1.0.0rc1       Release candidate
  1.0.0.post1    Post-release (e.g., packaging fix only)
  1.0.0.dev1     Development snapshot (not for PyPI)

MAJOR.MINOR.PATCH

MAJOR: Breaking API change (remove/rename public function/class/arg)
MINOR: New feature, fully backward-compatible
PATCH: Bug fix, no API change

# How it works:
git tag v1.0.0          →  installed version = 1.0.0
git tag v1.1.0          →  installed version = 1.1.0
(commits after tag)     →  version = 1.1.0.post1  (suffix stripped for PyPI)

# In code — NEVER hardcode when using setuptools_scm:
from importlib.metadata import version, PackageNotFoundError
try:
    __version__ = version("your-package")
except PackageNotFoundError:
    __version__ = "0.0.0-dev"    # Fallback for uninstalled dev checkouts

[tool.setuptools_scm]
version_scheme = "post-release"
local_scheme   = "no-local-version"   # Prevents +g<hash> from breaking PyPI uploads

# your_package/__init__.py
__version__ = "1.0.0"    # Update this before every release

# In [project] dependencies:
"httpx>=0.24"            # Minimum version — PREFERRED for libraries
"httpx>=0.24,<1.0"       # Upper bound only when a known breaking change exists
"httpx==0.27.0"          # Pin exactly ONLY in applications, NOT libraries

# NEVER do this in a library — it breaks dependency resolution for users:
# "httpx~=0.24.0"        # Too tight
# "httpx==0.27.*"        # Fragile

# 1. Update CHANGELOG.md — move [Unreleased] entries to [x.y.z] - YYYY-MM-DD
# 2. Commit the changelog
git add CHANGELOG.md
git commit -m "chore: prepare release vX.Y.Z"
# 3. Tag and push — this triggers publish.yml automatically
git tag vX.Y.Z
git push origin main --tags
# 4. Monitor GitHub Actions → verify on https://pypi.org/project/your-package/