python

At the start of every response, say "APPLIED PYTHON RULE".

Python Language Rule

Key Principles

• Write concise, technical Python code with accurate examples.
• Use functional programming; prefer functions over classes where possible.
• Prefer iteration and modularization over code duplication.
• Use descriptive variable names with auxiliary verbs (e.g., is_active, has_permission).
• Use lowercase_with_underscores for variables, functions, and file names.
• Follow PEP 8 style guidelines.

Python Language Guidelines

• Use def for functions, async def for asynchronous operations.
• Use type hints for all function signatures and variables where helpful.
• Use f-strings for string formatting.
• Prefer list/dict comprehensions over loops when readable.
• Use with statements for resource management (files, connections).
• Use *args and **kwargs appropriately for flexible function signatures.

Code Style (Ruff Configuration)

Follow these ruff settings for consistent style:

• Line length: 120 characters
• Target Python version: 3.9+
• Enable: pycodestyle errors/warnings (E, W), pyflakes (F), isort (I), flake8-comprehensions (C), flake8-bugbear (B)
• Known first-party imports: ["src"]
• Combine imports as single statements and force sort within sections
• __init__.py files should only contain docstrings - no imports or all declarations

Error Handling

• Handle errors and edge cases at the start of functions (guard clauses).
• Use early returns for error conditions; avoid deep nesting and unnecessary else.
• Place the happy path last in the function.
• Use specific exception types rather than bare except:.
• Implement proper exception handling with meaningful error messages.
• Use try/except/finally blocks appropriately.
• Keep try-catch blocks minimal - cover only the specific operations that can fail.

Code Structure

• Put constants (strings, string templates, etc.) at the top of the file after imports.
• Always use absolute imports - never use relative imports (e.g., use from src.module import Class not from .module import Class).
• Import standard library modules first, then third-party, then local imports.
• Caller should come before callee - define functions before they are called.
• Use docstrings for functions and classes following PEP 257.
• Keep functions small and focused on a single responsibility.
• Use meaningful function and variable names that explain intent.
• Avoid global variables; pass data through function parameters.