How to build distributions?

How to build Python distributions

This tutorial explains how to package your Python project and create distributions that can be easily installed by others.

Packaging your Python project is crucial for sharing your code with the wider community and making it easily accessible via package managers like pip.

Introduction to Python Distributions

Introduction to Python Distributions

Python distributions are packaged versions of your Python project that include all the necessary code, dependencies, and metadata needed for installation and usage.

There are two main types of distributions:

1. Source Distributions (sdist): Contains the source code of your project along with setup scripts. Users need to build the distribution from source.
2. Wheel Distributions (wheel): A pre-built distribution format that is faster to install as it doesn't require compilation.

We'll focus on using setuptools and wheel to create these distributions.

Project Setup: `setup.py` and `pyproject.toml`

Project Setup

Before you can build distributions, you need to set up your project with a setup.py file and a pyproject.toml file.

setup.py is the traditional build script for Python projects. It contains metadata about your project (name, version, author, etc.) and instructions on how to install it.

pyproject.toml is a configuration file that specifies build system requirements. It's used by tools like build to build distributions.

Example setup.py:

from setuptools import setup, find_packages

setup(
    name='my_package',
    version='0.1.0',
    packages=find_packages(include=['my_package', 'my_package.*']),
    install_requires=[
        'requests',
        'beautifulsoup4'
    ],
    author='Your Name',
    author_email='your.email@example.com',
    description='A short description of your package',
    long_description=open('README.md').read(),
    long_description_content_type='text/markdown',
    url='https://github.com/yourusername/my_package',
    classifiers=[
        'Programming Language :: Python :: 3',
        'License :: OSI Approved :: MIT License',
        'Operating System :: OS Independent',
    ],
    python_requires='>=3.6',
)

Explanation:

• name: The name of your package.
• version: The version of your package.
• packages: A list of packages to include in the distribution. find_packages() automatically finds all packages in your project directory.
• install_requires: A list of dependencies required by your package. pip will automatically install these when your package is installed.
• author, author_email, description, long_description, url: Metadata about your package and its author.
• classifiers: Metadata that helps categorize your package on PyPI.
• python_requires: Specifies the minimum Python version required by your package.

Example pyproject.toml:

[build-system]
requires = ["setuptools>=61.0", "wheel"]
build-backend = "setuptools.build_meta"

Explanation:

• requires: Specifies the build dependencies.
• build-backend: Specifies the build backend to use.

Building Source Distribution (sdist)

Building a Source Distribution (sdist)

A source distribution contains the source code of your project and the necessary metadata to build the package. It's created using the sdist command.

Steps:

1. Open your terminal and navigate to the root directory of your project (the directory containing setup.py).
2. Run the following command: python setup.py sdist

This command will create a dist directory containing a .tar.gz file. This is your source distribution.

Example output:

creating my_package-0.1.0
creating my_package-0.1.0/my_package
copying my_package-0.1.0/README.md -> my_package-0.1.0
copying my_package-0.1.0/setup.py -> my_package-0.1.0
copying my_package-0.1.0/my_package/__init__.py -> my_package-0.1.0/my_package
...other files...
gzip compressing dist/my_package-0.1.0.tar.gz
writing manifest file 'my_package-0.1.0.egg-info/SOURCES.txt'

python setup.py sdist

Building Wheel Distribution (wheel)

Building a Wheel Distribution (wheel)

A wheel distribution is a pre-built distribution format that is faster to install than a source distribution. It's created using the bdist_wheel command.

Steps:

1. Make sure you have the wheel package installed. If not, install it using: python -m pip install wheel
2. Open your terminal and navigate to the root directory of your project.
3. Run the following command: python setup.py bdist_wheel

This command will create a dist directory containing a .whl file. This is your wheel distribution.

Example output:

running bdist_wheel
running build
running build_py
creating build
creating build/lib
creating build/lib/my_package
copying my_package/__init__.py -> build/lib/my_package
...other files...
running install_lib
creating build/bdist.linux-x86_64/wheel
creating build/bdist.linux-x86_64/wheel/my_package
copying build/lib/my_package/__init__.py -> build/bdist.linux-x86_64/wheel/my_package
...other files...
creating build/bdist.linux-x86_64/wheel/my_package-0.1.0.dist-info
... other files...
creating 'dist/my_package-0.1.0-py3-none-any.whl' and adding 'build/bdist.linux-x86_64/wheel' to it
adding 'my_package/__init__.py'...
...other files...
adding 'my_package-0.1.0.dist-info/METADATA'
adding 'my_package-0.1.0.dist-info/WHEEL'
adding 'my_package-0.1.0.dist-info/top_level.txt'
adding 'my_package-0.1.0.dist-info/RECORD'
removing build/bdist.linux-x86_64/wheel

python -m pip install wheel
python setup.py bdist_wheel

Using `build` for Distribution Creation (Recommended)

Using the build Package (Recommended)

The build package provides a modern and standardized way to build Python distributions. It simplifies the process and ensures compatibility with different build backends.

Steps:

1. Install the build package: python -m pip install build
2. Navigate to the root directory of your project.
3. Run the following command: python -m build

This command will build both a source distribution and a wheel distribution and place them in the dist directory.

The build package uses the pyproject.toml file to determine the build backend and its requirements. This makes the build process more declarative and less dependent on specific build scripts.

Example output:

 * Building sdist
... (build output for sdist) ...
 * Building wheel
... (build output for wheel) ...

python -m pip install build
python -m build

Uploading to PyPI

Uploading to PyPI

Once you have built your distributions, you can upload them to the Python Package Index (PyPI) so that others can install them using pip.

Steps:

1. Install twine: python -m pip install twine. Twine is a tool for securely uploading packages to PyPI.
2. Register an account on PyPI (if you don't already have one).
3. Run twine upload dist/* from your project's root directory. Twine will prompt you for your PyPI username and password.

Important: For testing, consider using the Test PyPI server. You can upload your packages to Test PyPI using the --repository testpypi option with Twine. This will prevent your test packages from polluting the main PyPI index.

Example command for uploading to Test PyPI:

twine upload --repository testpypi dist/*

Make sure you have created a .pypirc file in your home directory with the credentials for Test PyPI if you are using it. The contents of the .pypirc file should look like this:

[distutils]
index-servers =
    pypi
    testpypi

[pypi]
username = your_pypi_username
password = your_pypi_password

[testpypi]
username = your_test_pypi_username
password = your_test_pypi_password

After uploading, your package will be available on PyPI and can be installed using pip install my_package.

python -m pip install twine
twine upload dist/*

Concepts behind the snippet

Concepts Behind Distribution Building

Building Python distributions involves understanding the roles of key components like setuptools, wheel, and twine.

• setuptools: A library designed to facilitate packaging Python projects. It provides tools for defining project metadata, managing dependencies, and building distributions.
• wheel: A package format designed to improve the installation speed and reliability of Python packages. Wheels are pre-built distributions, meaning they don't require compilation during installation.
• twine: A secure tool for publishing Python packages to PyPI. It helps protect against man-in-the-middle attacks by ensuring that packages are uploaded over HTTPS and that their integrity is verified.
• pyproject.toml: Configuration file for Python build tools, specifying build system requirements and other project settings.

Real-Life Use Case Section

Real-Life Use Case

Imagine you've developed a Python library for analyzing financial data. You want to share this library with your colleagues and the broader data science community. By creating a distribution, you make it easy for others to install and use your library without having to manually copy files or manage dependencies.

Another common use case is deploying Python applications to production environments. Packaging your application as a distribution ensures that all dependencies are correctly installed and that the application can be easily deployed and updated.

Best Practices

Best Practices for Building Distributions

• Use a virtual environment: Always create and activate a virtual environment before building your distributions. This will prevent your system's global Python installation from being polluted with development dependencies.
• Keep your setup.py file clean and well-documented: Make sure your setup.py file includes all necessary metadata and dependencies. Add comments to explain the purpose of each section.
• Include a README file: The README file should provide a clear and concise description of your package, as well as instructions on how to install and use it.
• Use a LICENSE file: Include a LICENSE file to specify the terms under which your package can be used and distributed.
• Test your distributions: Before uploading your distributions to PyPI, install them in a clean virtual environment and verify that they work as expected.
• Automate the build and upload process: Use tools like tox or CI/CD pipelines to automate the process of building and uploading your distributions.

Interview Tip

Interview Tip

When asked about packaging and distribution in a Python interview, be prepared to discuss the different distribution formats (sdist and wheel), the tools used for building distributions (setuptools, build), and the process of uploading to PyPI (twine). Demonstrate your understanding of the importance of packaging for code sharing and deployment.

You can also mention the importance of using virtual environments and managing dependencies effectively.

When to use them

When to Build Distributions

You should build distributions whenever you want to share your Python code with others, whether it's for internal use within your organization or for public use on PyPI.

Building distributions makes your code more accessible, reusable, and maintainable. It also helps to ensure that your code can be easily deployed and updated in production environments.

Memory footprint

Memory Footprint Considerations

The memory footprint of your distributions depends on the size of your code, dependencies, and any data files included in the package. Wheel distributions generally have a smaller memory footprint than source distributions because they are pre-built and don't require compilation during installation.

To minimize the memory footprint of your distributions, consider the following:

• Use a minimal set of dependencies: Only include the dependencies that are absolutely necessary for your package to function.
• Optimize your code: Write efficient code that minimizes memory usage.
• Compress large data files: If your package includes large data files, compress them using tools like gzip or bzip2.

Alternatives

Alternatives to setuptools and wheel

While setuptools and wheel are the most common tools for building Python distributions, there are some alternatives:

• poetry: Poetry is a tool for dependency management and packaging in Python. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you.
• flit: Flit is a simple way to package Python packages. It takes your package name and optionally your version from the module you're packaging, and otherwise doesn't require you to specify anything that you haven't already.
• pdm: PDM is a modern Python package manager supporting PEP 517. It aims to bring the best practices of other languages to Python, including managing dependencies and packaging.

Pros and Cons of using distributions

Pros and Cons of Building Distributions

Pros:

• Easy installation: Distributions can be easily installed using pip.
• Dependency management: Distributions allow you to declare dependencies, which are automatically installed when the package is installed.
• Code sharing: Distributions make it easy to share your code with others.
• Reusability: Properly packaged code is easier to reuse in other projects.
• Deployment: Facilitates easier and more reliable deployment to various environments.

Cons:

• Initial setup: Creating the setup.py and pyproject.toml files can be time-consuming.
• Learning curve: Understanding the different distribution formats and build tools can be challenging.
• Maintenance: You need to keep your setup.py file up-to-date as your project evolves.