How to Manage Python Dependencies and Environments with Poetry

Did you know that setting up a Python project locally can quickly become a crisis due to different operating systems, Python versions, and poor dependency management? I can't imagine that hassle, especially in large projects.

But here's a personal favourite Solution: Use Poetry, a modern tool for dependency management and packaging in Python.

Python 3.7+ Required

Step 1: Install Poetry Globally

Install Poetry with:

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

Step 2: Initialize a New Project

Create a new project:

poetry new demo_project
cd demo_project

This creates a directory structure like:

.
├── demo_project
│   └── __init__.py
├── pyproject.toml
├── README.md
└── tests
    └── __init__.py

Step 3: Add Dependencies

To add dependencies, such as requests and flask:

poetry add requests flask

Your pyproject.toml will update to include:

[tool.poetry]
name = "demo-project"
version = "0.1.0"
description = "Demonstrating how to manage Python dependencies and environments with Poetry."
authors = ["Joseph"]
readme = "README.md"

[tool.poetry.dependencies]
python = "^3.11"
requests = "^2.32.3"
flask = "^3.0.3"


[build-system]
requires = ["poetry-core"]
build-backend = "poetry.core.masonry.api"

Step 4: Install All Dependencies

Install all dependencies specified in your pyproject.toml:

poetry install

Step 5: Activate the Virtual Environment

Activate your project’s virtual environment:

poetry shell

Step 6: Remove a Dependency

To remove a dependency like flask:

poetry remove flask

This updates your pyproject.toml and poetry.lock files automatically.

Step 7: Let's set-up a simple flask app

In the demo_project folder, create a main.py file and paste in the following:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    return "Home page, yes?"

def main():
    app.run(debug=True)

if __name__ == '__main__':
    main()

Your folder structure should now look like so:

.
├── demo_project
│   ├── __init__.py
│   └── main.py
├── pyproject.toml
├── README.md
└── tests
    └── __init__.py

Step 8: Define and Run a Script

Add a script to your pyproject.toml under [tool.poetry.scripts]:

[tool.poetry.scripts]
app = 'demo_project.main:main'

As such, your configuration will look something like this:

[tool.poetry]
name = "demo-project"
version = "0.1.0"
description = "Demonstrating how to manage Python dependencies and environments with Poetry."
authors = ["Joseph"]
readme = "README.md"

[tool.poetry.dependencies]
python = "^3.11"
requests = "^2.32.3"
flask = "^3.0.3"


[build-system]
requires = ["poetry-core"]
build-backend = "poetry.core.masonry.api"

[tool.poetry.scripts]
app = 'demo_project.main:main'

Run your application with:

poetry run app

Conclusion

These examples demonstrate how Poetry simplifies Python project management, particularly with dependency handling. I hope you found this blog helpful!

Thank you for reading and happy Coding!