Python Development

Expert knowledge for modern Python development with focus on fast tooling, type safety, and comprehensive testing.

Core Expertise

• uv: Fast package management and Python environment handling (10-100x faster than pip)
• ruff: Ultra-fast linting and code formatting (replaces black, isort, flake8)
• pytest: Comprehensive testing with fixtures, parametrization, and coverage
• Type Hints: Static type checking with mypy/pyright integration
• pyproject.toml: Modern Python project configuration with dependency groups

Key Capabilities

• Project Setup: Modern project structure with uv and pyproject.toml
• Code Quality: Linting with ruff, formatting, type checking
• Testing: Unit tests, integration tests, parametrization, coverage tracking
• Dependencies: Package management with uv, dependency groups for dev/docs/security
• CI Integration: Automated testing and quality checks
• Debugging: Python-specific debugging with pdb, profiling, and memory analysis

Python Debugging Expertise

Interactive Debugging

• pdb/ipdb: Step-through debugging with breakpoints and inspection
• pytest --pdb: Drop into debugger on test failures
• Django Debug Toolbar: Web application debugging and profiling
• Flask Debug Mode: Development server with auto-reload and debugger

Performance & Memory Profiling

• memory_profiler: Line-by-line memory consumption analysis
• py-spy: Sampling profiler for production Python programs
• cProfile/profile: Built-in CPU profiling modules
• line_profiler: Line-by-line execution time analysis
• tracemalloc: Memory allocation tracking (built-in)

Debugging Commands

# Interactive debugging
python -m pdb script.py                # Start with debugger
pytest --pdb                           # Debug on test failure

# Memory profiling
python -m memory_profiler script.py    # Memory usage per line
py-spy top -- python script.py        # Real-time CPU profiling

# Performance profiling
python -m cProfile -s cumtime script.py | head -20
python -m trace --trace script.py     # Trace execution

Modern uv Workflow

Project Initialization

# Create new project with modern structure
uv init my-project --package          # Creates src/ layout project
cd my-project

# Create venv and install
uv venv
uv sync                               # Install from uv.lock

# Add dependencies
uv add requests pydantic              # Runtime dependencies
uv add --dev pytest ruff mypy        # Development dependencies
uv add --group docs sphinx            # Dependency groups

Dependency Management

# Add with version constraints
uv add "fastapi>=0.100.0,<1.0.0"
uv add "sqlalchemy[postgresql]"

# Update and sync
uv lock --upgrade                     # Update lockfile
uv sync --frozen                      # Install exact versions

# Run application
uv run app.py

Essential Commands

# Code quality
uv run ruff check --fix .               # Lint and auto-fix
uv run ruff format .                    # Format code
uv run mypy .                           # Type checking

# Testing
uv run pytest                          # Run tests
uv run pytest --cov                    # With coverage
uv run pytest -v --tb=short           # Verbose output

# Building and publishing
uv build                               # Build package
uv publish --token $PYPI_TOKEN        # Publish to PyPI

Best Practices

Project Structure (src layout)

my-project/
├── pyproject.toml
├── uv.lock
├── README.md
├── src/
│   └── my_awesome_project/
│       ├── __init__.py
│       ├── main.py
│       └── utils.py
└── tests/
    ├── test_main.py
    └── test_utils.py

Type Hints (Python 3.10+)

def process_data(
    items: list[str],                    # Use list[T] not List[T]
    config: dict[str, int],              # Use dict[K, V]
    optional_param: str | None = None,   # Use | not Union
) -> tuple[bool, str]:
    """Process data with modern type hints."""
    return True, "success"

Testing with pytest

import pytest

@pytest.fixture
def sample_data():
    return {"key": "value"}

@pytest.mark.parametrize("input,expected", [
    ("hello", "HELLO"),
    ("world", "WORLD"),
])
def test_uppercase(input: str, expected: str) -> None:
    assert input.upper() == expected

For detailed pyproject.toml configuration, advanced debugging patterns, CI/CD integration, and troubleshooting, see REFERENCE.md.