Dependency Management with Poetry

Introduction

In this post, I am going talk about managing dependency for python applications using Poetry.

What is 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. Poetry offers a lockfile to ensure repeatable installs, and can build your project for distribution” [Poetry Website].

Basically it does the work of pip (python package manager) and virtualenv(dependency management and virtualenv) all together.

Why shift from virtualenv to Poetry?

In a previous post, I briefly talked about version control and dependency management in python using virtualenv. However, I got to work on a new project as a backend developer, project ‘TOYKI’, with my college colleague. ‘TOYKI’ is a service that provides opportunities to overcome the limitations of offline human relationships and enables everyone to build social networks more easily. Learn more in our website.

TOYKI project is larger in scale compared to my previous projects, and more people will be working on it. So we seeked for a more professional and handy tool, and found Poetry. The handy features of Poetry, such as

1. automatically updating pyproject.toml file
2. the poetry.lock file
3. Integration of package management and virtualenv.

and more, made us use it for our version control.

Install

Please refer to official documentation

• https://python-poetry.org/docs/#installing-with-the-official-installer

If you already have pip in your device,

• pip install poetry

You can also install using curl,

• curl -sSL https://install.python-poetry.org | python3 -
• In linux/Unix, it will be stored in ~/.local/share/pypoetry
• You might need to manually add it to PATH in your .bashrc or .bash_profile file.
  • export PATH="$HOME/.local/share/pypoetry:$PATH"

Virtual Environment

You can create a virtual environment using Poetry as well. By default, the .venv file will be stored in the home directory. However, I prefer the .venv file to be in project folder.

• poetry config virtualenvs.in-project true

Now you have to activate the virtual environment.

• poetry shell

Other commands

• python -m poetry env list -> show all the list of venvs in your pwd or above. However, if you set the path for .venv file to be in your project-folder, this command is practically useless.
• python3 -m poetry env remove path
• python3 -m poetry env info -> show the info about the venv

Basics

Create new project

python3 -m poetry new project_name

This will create a new directroy from your current working directory with your project_name.

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

pyproject.toml

pyproject.toml: file stores the information about the dependencies/packages. It’s just like requirements.txt file. The difference is that it will get automatically updated.

Add&Install dependency

If you have a pre-configured pyproject.toml file, and want to install dependencies stated in the pyproject.toml file,

• python poetry install

poetry.lock

When you first run this command without a pre-configured poetry.lock file that was written previously by other developers, then it will create one for you.

• poetry.lock: this file stores the information about the dependencies/packages that should not be automatically installed with latest version when using python poetry install. By default, poetry will install the latest versions of the packages in the pyproject.toml file when you run python poetry install without a poetry.lock file. It ensures that everybody is using the exact same version of the dependencies!

If you want to add/remove a dependency or python package,

• python poetry add package_name
• python poetry add "package_name=version.version.version"
• python poetry remove package_name

Other Basics

• python poetry show -> show all the packages

Written by

Roger Kim