google-python-style-guide-pep-8-google-extensions

name	Google Python Style Guide (PEP 8 + Google Extensions)
description	Apply Python best practices, conventions, and style rules from Google's Python Style Guide. Use when writing, reviewing, or refactoring Python code to ensure clean, maintainable, and Pythonic implementations.

Google Python Style Guide

Apply best practices and conventions from the official Google Python Style Guide to write clean, idiomatic Python code.

When to Apply

Use this skill automatically when:

• Writing new Python code
• Reviewing Python code
• Refactoring existing Python implementations

Important: PEP 8 Takes Precedence

When Google's style guide conflicts with PEP 8, always follow PEP 8. PEP 8 is the official Python style guide and is the canonical source for Python coding conventions. Google's guide extends and clarifies PEP 8 but should not override it.

Common areas where conflicts may occur:

• Line length (PEP 8: 79 chars, Google: 80-100 chars) → Use Google style (project standard)

Key Reminders

Follow the conventions and patterns documented at https://google.github.io/styleguide/pyguide.html, with particular attention to:

Imports

• Use import statements for packages and modules only
• Use from x import y where x is the package prefix and y is the module name with no prefix.
• Import each module using the full pathname location
• Avoid from module import *
• Order: standard library, third-party, local application imports

Naming Conventions

• module_name, package_name, ClassName, method_name, ExceptionName
• function_name, GLOBAL_CONSTANT_NAME, global_var_name, instance_var_name
• function_parameter_name, local_var_name
• Single leading underscore _ for internal use
• Avoid single letter names except for counters/iterators

Documentation

• Use docstrings for all public modules, functions, classes, and methods
• Follow Google docstring format with Args, Returns, Raises sections
• First line should be a one-line summary
• Example:

  def fetch_data(source: str, limit: int = 100) -> list[dict]:
      """Fetches data from the specified source.
  
      Args:
          source: The data source URL or path.
          limit: Maximum number of records to fetch.
  
      Returns:
          A list of dictionaries containing the fetched data.
  
      Raises:
          ValueError: If source is empty or invalid.
      """
  

Type Annotations

• Use type hints for function signatures (Python 3.9+)
• Annotate public APIs
• Use typing module for complex types
• Prefer specific types over Any

Error Handling

• Use specific exceptions, not bare except:
• Minimize code in try/except blocks
• Use finally for cleanup actions
• Prefer standard exceptions over custom ones

Code Organization

• Maximum line length: 100 characters (Google standard, per project configuration)
• Use 4 spaces for indentation (never tabs)
• Two blank lines between top-level definitions
• One blank line between method definitions

Best Practices

• Comprehensions: Use for simple cases; avoid complex nested comprehensions
• Generators: Prefer generators over lists for large datasets
• Lambda: Use only for one-liners; use def for anything more complex
• Default Arguments: Never use mutable objects as default values
• Properties: Use @property for accessing/setting attributes with logic
• Context Managers: Use with statements for resource management
• String Formatting: Prefer f-strings (Python 3.6+) or str.format()

Anti-Patterns to Avoid

• Global variables (except constants)
• Mutable default arguments: def foo(x=[]): ❌
• Wildcard imports: from module import * ❌
• Bare except clauses: except: ❌
• Using deprecated features (e.g., % string formatting)

References

• Official Guide: https://google.github.io/styleguide/pyguide.html
• PEP 8: https://peps.python.org/pep-0008/
• Python Documentation: https://docs.python.org/3/