Modern Python Development on macOS: Fast and Isolated with UV

Why This Matters

Python is the “duct tape” of DevOps, but its environment management is notoriously complex. macOS comes with a “System Python” that you should never touch, as modifying it can break core OS functions.

The traditional way to manage Python (using pyenv, pip, and virtualenv) is slow and often results in “dependency hell.” By using UV, a modern Python manager written in Rust, you get a single tool that handles everything—Python versions, virtual environments, and global CLI tools—at speeds that are 10-100x faster than traditional methods.

Key Benefits

• Isolation: Keep your system clean. Every project and tool gets its own space.
• Speed: Install dependencies in milliseconds, not minutes.
• Simplicity: One tool (uv) replaces three or four legacy ones.

1. Installing UV: The Only Tool You Need

Instead of installing Python directly, we install uv, which will then manage Python for us.

brew install uv

Why UV?

• It acts as a Python installer (replaces pyenv).
• It acts as a package installer (replaces pip).
• It acts as a tool manager (replaces pipx).

2. Managing Python Versions

Need a specific version for a project? UV makes it trivial.

# Install the latest Python
uv python install 3.14

# List all available and installed versions
uv python list

Pro-Tip: Setting Your Default

If you want python3 in your terminal to always point to a UV-managed version, add a symlink in your ~/.local/bin (which should be in your PATH):

ln -sfn "$(uv python find 3.14)" ~/.local/bin/python3

3. Isolated CLI Tools (Ansible & More)

One of UV’s best features is its ability to install CLI tools (like Ansible or Ruff) in their own hidden virtual environments, so they never conflict with each other.

Installing Ansible Correctly

uv tool install --with-executables-from ansible-core,ansible-lint ansible

Why this is better?

• Ansible is now available globally.
• It has its own private Python environment.
• You can upgrade it with uv tool upgrade ansible without affecting anything else.

❯ uv tool list
ansible v8.7.0
- ansible-community
basedpyright v1.39.3
- basedpyright
- basedpyright-langserver
ruff v0.15.11
- ruff

4. Per-Project Virtual Environments

When you start a new project, UV makes environment creation instantaneous.

# Create a venv and sync dependencies from pyproject.toml
uv venv
source .venv/bin/activate
uv sync

Automatic Activation with Direnv

If you followed the Secrets and Environment guide, you can automate this even further. You don’t need to manually source .venv/bin/activate if you use direnv.

Simply add this to your project’s .envrc:

# .envrc
layout uv

layout_uv() {
  export VIRTUAL_ENV=${VIRTUAL_ENV:-$(pwd)/.venv}
  if [[ ! -d $VIRTUAL_ENV ]]; then
    uv venv
  fi
  PATH_add "$VIRTUAL_ENV/bin"
}

Now, whenever you cd into the project, direnv will automatically create the virtual environment (if it doesn’t exist) and activate it for you. This is the cleanest way to work across multiple Python projects.

5. Best Practices for Python on macOS

1. Rule Zero: Never sudo pip install.
2. Use .python-version: Place this file in your project root, and uv will automatically use the correct version.
3. Automate with UV Run: You can run a script without even creating a venv using uv run script.py. It will handle dependencies on the fly.

Summary

You now have a blazingly fast, modern Python setup that keeps your macOS system pristine. Your automation tools are isolated, and your projects are reproducible. Now that we can automate, let’s look at the Cloud and Kubernetes toolkit.