Fun with uv and PEP 723

Summary

Fun with uv and PEP 723 June 24, 2025 For the longest time, I have been frustrated with Python because I couldn’t use it for one-off scripts. I had to first ensure it was running in an environment where it could find the right Python version and the dependencies installed. That is now a thing of the past. If you are not a Pythonista (or one possibly living under a rock), uv is an extremely fast Python package and project manager, written in Rust. uv also provides this nifty tool called uvx (kinda like npx from the Node/NPM ecosystem for Javascript/Typescript packages) which can be used to invoke a Python tool inside a package. uvx takes care of creating a (cached) disposable virtual environment, setting up the right Python version and installing all the dependencies before running. For example $ uvx ruff --version Installed 1 package in 5ms ruff 0.12.0 PEP 723 is a Python Enhancement Proposal that specifies a metadata format that can be embedded in single-file Python scripts to assist launchers, IDEs and other external tools which may need to interact with such scripts. Here is the example directly lifted from the proposal: # /// script # requires-python = ">=3.11" # dependencies = [ # "requests<3", # "rich", # ] # /// import requests from rich.pretty import pprint resp = requests.get("https://peps.python.org/api/peps.json") data = resp.json() pprint([(k, v["title"]) for k, v in data.items()][:10]) Combining uv and the PEP-723 metadata inside a Python script, we can run the script in the previous section as follows: $ uv run pep.py Installed 9 packages in 24ms [ │ ('1', 'PEP Purpose and Guidelines'), │ ('2', 'Procedure for Adding New Modules'), │ ('3', 'Guidelines for Handling Bug Reports'), │ ('4', 'Deprecation of Standard Modules'), │ ('5', 'Guidelines for Language Evolution'), │ ('6', 'Bug Fix Releases'), │ ('7', 'Style Guide for C Code'), │ ('8', 'Style Guide for Python Code'), │ ('9', 'Sample Plaintext PEP Template'), │ ('10', 'Voting Guidelines') ] We can comb...