Poetry: Tool to resolve the Python dependencies

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First off, lets talk about the challenges of Dependency Management

Let’s look at a real-life situation:

• Imagine you’re working on a Python project that started small. Maybe you were working on using an LLM in an AI project, but it grew into something significant, like using multiple models to handle different use cases.
• You must have added several packages and libraries to your project, each for a different feature. At first, everything works fine. But as time goes by, you notice that updating one package breaks another.
• You try to install a new package, and suddenly your project is flooded with version conflicts. This is the dark side of dependency management—when a simple pip install spirals into hours of troubleshooting.

This isn’t just a theoretical problem. I faced this while working on a data science project. The dependencies were growing, and maintaining them became a nightmare. The project relied on several data processing and machine learning libraries, each with its own set of dependencies. A single update to one package caused a cascade of issues, and I spent days trying to resolve conflicts. I knew there had to be a better way.

What is Poetry? Where to Get It and How to Use It in Development

Poetry is a dependency management and packaging tool for Python that helps manage project dependencies efficiently. It ensures that all dependencies are specified and maintained in a single file (pyproject.toml) and simplifies the whole process of adding, updating, or removing dependencies.

To install Poetry, you can use the following commands:

pip install poetry

Or, you can try this as well:

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

Once installed, using Poetry is straightforward. It helps you create a new project, manage dependencies, and even build and publish your Python packages. Here’s how you can create a new project with Poetry:

poetry new my-awesome-project
cd my-awesome-project
poetry add requests

In just a few steps, you’ve set up a new project with dependencies neatly managed by Poetry.

How Poetry Works

Poetry is designed to simplify the management of dependencies, virtual environments, and project configurations. Here’s a breakdown of how it works and why it’s so effective:

When you create a new project with Poetry, it generates a pyproject.toml file. This file is the central configuration file for your project. It includes all the information about your project, such as its name, version, dependencies, and any specific settings for build tools or plugins.

Sample pyproject.toml file:

[tool.poetry]
name = "web-scraper"
version = "0.1.0"
description = "A simple web scraper"
authors = ["Soumya Sourav <email@example.com>"]

[tool.poetry.dependencies]
python = "^3.8"
requests = "^2.25.1"
beautifulsoup4 = "^4.9.3"

This file is the backbone of your project. Whenever you add, update, or remove a dependency, Poetry updates this file to reflect the changes.

Dependency Resolution and Locking

One of the most powerful features of Poetry is its ability to resolve dependencies and lock them to specific versions. When you add a dependency using poetry add, Poetry analyzes all potential versions of the package and its dependencies to find a combination that works together without conflicts.

After resolving the dependencies, Poetry creates a poetry.lock file. This file is a snapshot of all the exact versions of the dependencies used in your project. This ensures that every time you or someone else installs the project, the same versions of the dependencies are used, eliminating the “works on my machine” problem.

poetry lock #This command locks your dependencies

Virtual Environments for Isolation

Poetry automatically creates a virtual environment for your project. This is a key feature because it isolates your project’s dependencies from other projects on your machine. This means you can have multiple projects, each with different dependencies, without them interfering with each other.

By default, Poetry manages the virtual environment in the background, but you can always check where it’s located using:

poetry env info --path

You can also activate the environment manually if you need to:

poetry shell

Bettered Project Management

Poetry isn’t just about managing dependencies—it also helps with other aspects of project management. For instance, it can automatically generate the scaffolding for a new Python project, handle version bumps, and even publish your package to PyPI (Python Package Index).

Here’s how you can bump the version of your project:

poetry version patch

And if you’re ready to share your package with the world:

poetry publish

Easy Integration with Continuous Integration (CI) and Deployment Pipelines

Poetry’s clear and consistent management of dependencies makes it a great fit for CI/CD pipelines. When integrated with CI tools, Poetry ensures that all tests run against the exact same versions of dependencies, reducing the chances of encountering unexpected issues during deployment.

You can integrate Poetry in your CI pipeline by simply adding it to your CI configuration, ensuring that the environment is set up correctly before running tests or deployments:

poetry install
poetry run pytest

Sample Python Project Using Poetry

Let’s walk through a simple project to see Poetry in action. Imagine we’re building a small web scraper that extracts data from a website.

poetry new web-scraper
cd web-scraper

Next, we’ll add the required dependencies:

poetry add requests beautifulsoup4

Poetry will automatically resolve and lock the dependencies in the poetry.lock file, ensuring that everyone working on the project uses the exact same versions.

Now, let’s write a simple script using requests and beautifulsoup4 to scrape data:

import requests
from bs4 import BeautifulSoup

response = requests.get("https://example.com")
soup = BeautifulSoup(response.text, 'html.parser')

print(soup.title.text)

How to Deploy Applications on a Server

Deploying applications with Poetry is very easy. Once your project is complete, you can package it for deployment:

poetry build

This command creates a distributable package that you can deploy to any server. On the server, you can install your package using Poetry, ensuring that all dependencies are correctly set up:

poetry install

If you’re deploying a web application, you can use tools like Docker to containerize your application, including all dependencies managed by Poetry, and deploy it on cloud platforms like AWS or Azure.

Final Thoughts

Dependency management in Python doesn’t have to be a headache. Poetry simplifies the process, making it easier to manage, share, and deploy your projects without the fear of dependency hell. Whether you’re working on a small script or a large-scale application, Poetry can bring order to your project’s dependencies, saving you time and frustration. So, the next time you find yourself tangled in a web of package conflicts, remember that Poetry is there to help you bring harmony back to your development workflow.