Getting Started with Python Poetry: Dependency Management and Publishing

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Introduction

Python Poetry is a powerful tool for dependency management and packaging in Python. It simplifies package installation, dependency resolution, and publishing to PyPI. In this post, we’ll explore how to use Poetry, manage dependencies, understand versioning syntax, and publish a package.

Installing Poetry

To install Poetry, run the following command:

curl -sSL https://install.python-poetry.org | python3 -

After installation, add Poetry to your PATH:

export PATH="$HOME/.local/bin:$PATH"

To verify the installation, run:

poetry --version

Creating a New Project

To create a new Python project with Poetry, use:

poetry new my_project

This creates a my_project directory with a predefined structure:

my_project/
├── pyproject.toml
├── README.rst
├── my_project/
│   └── __init__.py
└── tests/

Managing Dependencies

Poetry simplifies dependency management using the pyproject.toml file.

Adding Dependencies

To add a dependency, use:

poetry add requests

This updates pyproject.toml and installs the dependency.

Adding Development Dependencies

For dependencies used in development (e.g., testing libraries like pytest), use:

poetry add --dev pytest

Installing Dependencies

If you clone a project that uses Poetry, install dependencies with:

poetry install

This installs both main and development dependencies.

Understanding Versioning in Poetry

Poetry uses semantic versioning (SemVer) and supports flexible version constraints:

  • ^1.2.3: Compatible with 1.x.y, where x >= 2
  • ~1.2.3: Compatible with 1.2.x, but < 1.3.0
  • 1.2.3: Exact version 1.2.3
  • >=1.2, <2.0: Custom range

Example:

dependencies = {
    "requests" = "^2.25.1"
}

This allows any 2.x version, but not 3.x.

Running Tests with Poetry

After adding pytest as a development dependency, run tests with:

poetry run pytest

Publishing to PyPI

To publish a package, follow these steps:

  1. Build the package:poetry build
  2. Publish to PyPI:poetry publish --username <your-username> --password <your-password>

For automated publishing, use a PyPI token:

poetry config pypi-token.pypi <your-token>
poetry publish

Conclusion

Poetry is a modern tool that simplifies dependency management, versioning, and publishing. By using Poetry, you can ensure consistent environments, easily manage dependencies, and streamline package distribution.

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