Local Speed, Smooth Deploys: Heroku Adds Support for uv

Summary

Heroku now natively supports uv, a Rust-written Python package manager presented as a faster alternative to pip for dependency resolution, installation, and virtual-environment management. The post connects this support to recurring problems in modern Python projects, including slow installs, complex dependency trees, version pinning, and tooling that may struggle to keep pace with current standards. It walks through installing uv, running uv init, adding Flask and Gunicorn with uv add, and deploying a basic Flask application using a Procfile, pyproject.toml, uv.lock, and .python-version. Heroku detects the Python app, installs dependencies from these project files, and starts it with gunicorn main:app after a Git push. The stated outcome is faster local development, more consistent environments, reduced onboarding time, fewer flaky builds, and improved pipeline performance, while uv remains relatively new.

Takeaways

1. 1

   uv is written in Rust and is described as significantly faster than pip for resolving and installing dependencies, particularly in large or complex projects.

2. 2

   Running uv add Flask and uv add gunicorn updates both pyproject.toml and uv.lock, combining declared dependencies with a lockfile for project management.

3. 3

   Heroku deployment uses Git push, reads .python-version, uv.lock, and pyproject.toml to install dependencies, then starts the app through the Procfile command.