function-design

Clean Python function design requires explicit dependencies, single responsibility, pure functions, and stable return types. You must pass dependencies as parameters, avoid global state, and ensure each function performs one focused task without mutating inputs.

Enforce Python coding standards by validating function signatures, parameter handling, and async patterns. Check for guard clauses to validate early, ensure command-query separation, and confirm functions raise exceptions instead of returning None for errors.

Raise exceptions for Python function errors and reserve None strictly for "not found" cases. This approach ensures return type stability, meaning your function returns the same type regardless of input, preventing unexpected type errors downstream.

Use async patterns in Python function design when functions involve I/O operations or concurrent tasks. Apply async conventions consistently during code review to ensure clear interfaces and proper argument handling without blocking execution.

Guard clauses improve Python functions by validating conditions early and returning or raising immediately. This keeps functions small and focused, preventing deep nesting and ensuring clear interfaces composed of focused helpers.

Command-query separation in Python code means a function should either perform an action or return data, not both. Following this standard ensures single responsibility, making functions easier to test, review, and compose into larger workflows.