Python Packaging

Packaging means converting your project into a reusable installable library.

        Purpose:
        - share code across projects
        - publish on PyPI
        - make installation easy: pip install yourpackage
        
        ## Recommended project structure
        
        ```
        mypackage/
        ├── mypackage/
        │   ├── __init__.py
        │   └── module.py
        ├── tests/
        ├── README.md
        ├── LICENSE
        └── pyproject.toml
        ```
        
        Note: modern Python uses **pyproject.toml** (recommended).
        
        ## Minimal pyproject.toml (modern standard)
        
        ```toml
        [build-system]
        requires = ["setuptools>=68", "wheel"]
        build-backend = "setuptools.build_meta"
        
        [project]
        name = "mypackage"
        version = "0.1.0"
        description = "A short description"
        readme = "README.md"
        requires-python = ">=3.9"
        dependencies = ["requests>=2.25.0"]
        ```
        
        ## __init__.py (clean exports)
        
        ```python
        from .module import function1, function2
        __all__ = ["function1", "function2"]
        __version__ = "0.1.0"
        ```
        
        ## Build package
        
        ```bash
        pip install build twine
        python -m build
        ```
        
        This creates files in `dist/`:
        - .whl (wheel)
        - .tar.gz (source)
        
        ## Upload to PyPI
        
        ```bash
        twine upload --repository testpypi dist/*
        # then real PyPI:
        twine upload dist/*
        ```
        
        ## Install package
        
        ```bash
        pip install mypackage
        pip install -e .  # editable install for development
        ```
        
        ## Graph: packaging lifecycle
        
        ```mermaid
        flowchart LR
          A[Write reusable code] --> B[Add pyproject.toml]
          B --> C[Build dist/]
          C --> D[Upload to PyPI]
          D --> E[Others install with pip]
        ```
        
        ## Remember
        
        - Packaging makes code reusable
        - Use pyproject.toml (modern)
        - Always include README and LICENSE
        - Test on TestPyPI first