GN

Google Python Style Guide Summary

This document summarizes key rules and best practices from the Google Python Style Guide.

1. Python Language Rules

  • Linting: Run pylint on your code to catch bugs and style issues.
  • Imports: Use import x for packages/modules. Use from x import y only when y is a submodule.
  • Exceptions: Use built-in exception classes. Do not use bare except: clauses.
  • Global State: Avoid mutable global state. Module-level constants are okay and should be ALL_CAPS_WITH_UNDERSCORES.
  • Comprehensions: Use for simple cases. Avoid for complex logic where a full loop is more readable.
  • Default Argument Values: Do not use mutable objects (like [] or {}) as default values.
  • True/False Evaluations: Use implicit false (e.g., if not my_list:). Use if foo is None: to check for None.
  • Type Annotations: Strongly encouraged for all public APIs.

2. Python Style Rules

  • Line Length: Maximum 80 characters.
  • Indentation: 4 spaces per indentation level. Never use tabs.
  • Blank Lines: Two blank lines between top-level definitions (classes, functions). One blank line between method definitions.
  • Whitespace: Avoid extraneous whitespace. Surround binary operators with single spaces.
  • Docstrings: Use """triple double quotes""". Every public module, function, class, and method must have a docstring.
    • Format: Start with a one-line summary. Include Args:, Returns:, and Raises: sections.
  • Strings: Use f-strings for formatting. Be consistent with single (') or double (") quotes.
  • TODO Comments: Use TODO(username): Fix this. format.
  • Imports Formatting: Imports should be on separate lines and grouped: standard library, third-party, and your own application's imports.

3. Naming

  • General: snake_case for modules, functions, methods, and variables.
  • Classes: PascalCase.
  • Constants: ALL_CAPS_WITH_UNDERSCORES.
  • Internal Use: Use a single leading underscore (_internal_variable) for internal module/class members.

4. Main

  • All executable files should have a main() function that contains the main logic, called from a if __name__ == '__main__': block.

BE CONSISTENT. When editing code, match the existing style.

Source: Google Python Style Guide