modern-python-tooling-part1.md

Modern Python Tooling — Part 1: uv and ruff

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The Python ecosystem has modernized significantly. This part covers uv and ruff — the two tools that replace most of the older pip/venv/black/flake8 toolchain.

uv — the fast Python package manager

uv is a single tool that replaces pip, venv, pip-tools, and pyenv. It is written in Rust, and it is extremely fast — often 10-100x faster than pip.

Installing uv

# macOS / Linux
curl -LsSf https://astral.sh/uv/install.sh | sh

# Windows (PowerShell)
powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

# Or with pip (works everywhere)
pip install uv

Creating a project with uv

# Create a virtual environment (replaces python -m venv .venv)
uv venv

# Activate it — same as before
# macOS/Linux:
source .venv/bin/activate
# Windows PowerShell:
.venv\Scripts\Activate.ps1
# Windows Git Bash:
source .venv/Scripts/activate

# Install packages (replaces pip install)
uv pip install requests flask pytest

# Install from requirements file (replaces pip install -r)
uv pip install -r requirements.txt

# Save dependencies (replaces pip freeze)
uv pip freeze > requirements.txt

The uv workflow

# 1. Create project folder.
mkdir my_project && cd my_project

# 2. Create virtual environment.
uv venv

# 3. Activate it.
source .venv/bin/activate    # or .venv\Scripts\Activate.ps1 on Windows

# 4. Install packages.
uv pip install requests pytest

# 5. Save dependencies.
uv pip freeze > requirements.txt

# 6. Work on your project...

# 7. When done, deactivate.
deactivate

Notice this is almost identical to the pip workflow — just replace pip with uv pip and python -m venv with uv venv.

Why uv over pip?

Feature	pip	uv
Install speed	Slow (downloads sequentially)	Fast (parallel, cached)
Dependency resolution	Basic	Advanced (like cargo/npm)
Virtual environments	Separate tool (python -m venv)	Built-in (uv venv)
Lock files	No (need pip-tools)	Built-in (uv lock)
Python version management	No (need pyenv)	Built-in (uv python)

If you prefer pip

All uv pip commands have pip equivalents. If uv is not available on your machine, replace:

uv venv          →  python -m venv .venv
uv pip install X  →  pip install X
uv pip freeze     →  pip freeze

The rest of the workflow stays the same.

ruff — the fast linter and formatter

ruff replaces flake8 (linter), black (formatter), and isort (import sorter) in a single tool.

Installing ruff

uv pip install ruff
# or
pip install ruff

Using ruff

# Check for problems (replaces flake8)
ruff check .

# Fix problems automatically
ruff check . --fix

# Format code (replaces black)
ruff format .

# Check formatting without changing files
ruff format . --check

Example

# before.py — has issues
import os
import sys
import os  # duplicate import
x=1  # missing spaces

def greet(name ):  # extra space
    print( f"Hello, {name}" )

$ ruff check before.py
before.py:3:1: F811 Redefinition of unused `os` from line 1

$ ruff check before.py --fix
Found 1 error (1 fixed, 0 remaining).

$ ruff format before.py
1 file reformatted.

After:

# before.py — cleaned up
import os
import sys

x = 1


def greet(name):
    print(f"Hello, {name}")

Configuring ruff

Add to pyproject.toml (the modern Python config file):

[tool.ruff]
line-length = 88  # Same as black default

[tool.ruff.lint]
select = ["E", "F", "I"]  # Errors, pyflakes, isort

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