Why Python developers should switch to uv

# The old way - multiple steps, slow process
mkdir new-project && cd new-project
python -m venv venv
source venv/bin/activate  # or venv\Scripts\activate on Windows
pip install package1 package2 package3
# Wait... and wait... for slow installations
pip freeze > requirements.txt

# Initialize project with everything configured
uv init "new-ai-project"

cd "new-ai-project"

# Add dependencies instantly
uv add openai pydantic fastapi

# Add development tools separately
uv add ipykernel pytest --dev

# Run your code
uv run hello.py

# Create new project with boilerplate
uv init "project-name"

# Add production dependencies
uv add requests pandas numpy

# Add development dependencies  
uv add pytest black flake8 --dev

# Remove packages
uv remove pandas

# Sync environment from pyproject.toml
uv sync

# Execute Python files directly
uv run script.py

# Run with environment automatically activated
uv run python -m pytest

brew install uv

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

uv --help

uv pip install -r requirements.txt

uv init --existing-project
uv add $(cat requirements.txt | grep -v '^#' | tr '\n' ' ')

# List available Python versions
uv python list

# Install specific Python version
uv python install 3.12

# Use specific version for project
uv init --python 3.12 my-project

my-python-app/
├── .upsun/
│   └── config.yaml
├── pyproject.toml  # Created by uv
├── main.py
└── src/

applications:
  app:
    source:
      root: "/"
    
    type: "python:3.12"
    
    # Use uv for dependency management
    dependencies:
      python3:
        uv: "*"
    
    # uv build process
    hooks:
      build: |
        # Use uv for fast dependency installation
        uv sync --frozen
        
        # Optional: compile Python files for better performance
        # python -m compileall .
    
    # Web server configuration
    web:
      commands:
        # We add --no-sync to prevent uv from trying to write the uv.lock at runtime 
        start: "uv run --no-sync uvicorn app:app --reload --host 0.0.0.0 --port $PORT"
    
    # uv cache optimization
    variables:
      env:
        uv_CACHE_DIR: "/tmp/uv-cache"
        PYTHONPATH: "."

routes:
  "https://{default}/":
    type: upstream
    upstream: "app:http"

uv init my-app
cd my-app
uv add fastapi gunicorn

# main.py
from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"message": "Hello from uv on Upsun!"}

git add .
git commit -m "Setup FastAPI with uv"
upsun push