Python Style Best Practices Skill

This skill automatically activates when writing Python code to ensure consistency with PEP standards, type hints, and modern Python idioms.

Core Standards

• PEP 8: Naming conventions, imports, line length
• Type Hints: Modern syntax (list[str] not List[str], X | None not Optional[X])
• Docstrings: Google style with Args, Returns, Raises sections
• Imports: stdlib → third-party → local, alphabetically sorted

Naming Conventions

# Classes: PascalCase
class UserAccount:
    pass

# Functions/variables: snake_case
def calculate_total():
    user_name = "john"

# Constants: SCREAMING_SNAKE_CASE
MAX_RETRY_COUNT = 3

# Private: single underscore prefix
def _internal_helper():
    pass

Type Hints (Python 3.10+)

# Use built-in generics
def process(items: list[str]) -> dict[str, int]:
    pass

# Use | for Optional/Union
def find_user(id: str) -> User | None:
    pass

# TypedDict for structured dicts
class UserData(TypedDict):
    id: str
    name: str

Function Length Guidelines

• < 30 lines: Ideal
• 30-50 lines: Review for refactoring
• > 50 lines: Must be broken down

Anti-Patterns to Avoid

• Missing type hints
• Bare except: clauses
• Magic numbers/strings without constants
• Non-expressive variable names (d, temp, x)
• Vague function names (process, handle, do_stuff)