4.15 Packaging

Packaging in Python refers to the process of bundling code into a distributable format that can be easily installed and used by others. A Python package typically contains a collection of Python modules, accompanied by metadata like package name, version, and dependencies. This makes it easier to manage, distribute, and install software libraries and applications.

Libraries Used for Packaging

  1. setuptools: The most widely used packaging library in Python. It includes functionalities for building, installing, and distributing Python packages.

  2. wheel: A built-package format for Python that provides faster installation compared to traditional source distributions.

  3. pip: Not a packaging library per se, but it’s the package installer for Python that works in conjunction with packaging libraries to install packages.

  4. twine: Utility for securely uploading packages to PyPI (Python Package Index).

  5. conda: A cross-platform package manager that can also handle Python packages. Often used in data science and scientific computing contexts.

  6. poetry: A more modern packaging tool that aims to improve package creation and management, with a focus on simplicity and being opinionated.

  7. flit: Simplified package creator that makes it easier to make a package out of simple Python modules.

The wheel format is a newer standard than the egg format, and is designed to replace the egg format. The wheel format is specified in PEP 427, and it has several advantages over the egg format and other previous packaging formats:

  • faster installation

  • fewer incompatibilities between Python versions

  • easier creation of packages

  • safer installation (no arbitrary code execution) - arbitrary code execution means that a user can run any code they want on your computer

  • consistent behavior across platforms

  • more consistent file naming and location conventions

  • less implementation complexity

Pros

  1. Reusability: Once a package is created, it can be easily shared, reused, and installed on other systems.

  2. Version Control: Packaging allows versioning, which helps in using and maintaining different versions of the same package.

  3. Dependency Management: Packages can specify dependencies, making it easier for users to install everything they need.

  4. Professionalism: Packaging your code makes it accessible and usable, which can be essential if you’re trying to share it for public consumption or even within a large organization.

Cons

  1. Complexity: The packaging process can be complex, especially for beginners or for projects with complex dependencies.

  2. Maintenance: Once a package is public, it requires ongoing maintenance to keep it updated and to fix bugs.

  3. Package Conflicts: Multiple packages might have conflicting dependencies, making package management challenging.

  4. Security Concerns: Public packages can be a vector for malware if not properly vetted.

Creating a simple package using setuptools

  1. Directory Structure

    my_package/
├── my_module.py
└── setup.py

  2. my_module.py: This file contains the actual Python code.

    def hello_world():
    return "Hello, world!"

  3. setup.py: This file contains metadata about your package.

    from setuptools import setup

setup(
    name="my_package",
    version="0.1",
    description="A simple package",
    author="Your Name",
    author_email="your.email@example.com",
    packages=["my_package"],
)

  4. Building the Package

Open the terminal, navigate to the directory containing setup.py, and run:

python setup.py sdist bdist_wheel
# This will create a source distribution (sdist) and a built distribution (bdist_wheel) under a dist/ directory.

  1. Installing the Package Locally

    pip install ./dist/my_package-0.1-py3-none-any.whl

  2. Using the Package

Now, in any Python script, you can do:

import my_package.my_module

print(my_package.my_module.hello_world())  # Output: Hello, world!

  1. Uploading to PyPI (Optional)

    # First, install twine:
pip install twine

# Then, upload your package:
twine upload dist/*

# You'll need a PyPI account, and you'll be prompted for your credentials during the upload process.