PEP 8 Code Style Standards

This rule applies to files matching the patterns above.

# PEP 8 Code Style Standards

## Rule
All Python code MUST comply with PEP 8 style guidelines. Use automated formatters (Black, Ruff) to enforce consistency. No manual formatting debates.

## Naming Conventions
| Element | Convention | Example |
|---------|-----------|---------|
| Module | snake_case | `user_service.py` |
| Class | PascalCase | `UserService`, `HTTPClient` |
| Function/Method | snake_case | `get_user_by_id()` |
| Variable | snake_case | `user_count`, `file_path` |
| Constant | UPPER_SNAKE_CASE | `MAX_RETRIES`, `DEFAULT_TIMEOUT` |
| Private | _prefix | `_internal_method()`, `_cache` |
| Protected | _prefix | `_validate()` |

## Good Examples
```python
"""User service module for managing user operations."""

from __future__ import annotations

import logging
from dataclasses import dataclass
from typing import Optional

logger = logging.getLogger(__name__)

MAX_LOGIN_ATTEMPTS = 5
DEFAULT_PAGE_SIZE = 20


@dataclass
class UserConfig:
    """Configuration for user service."""

    max_retries: int = 3
    timeout_seconds: float = 30.0


class UserService:
    """Service for managing user operations."""

    def __init__(self, config: UserConfig | None = None) -> None:
        self._config = config or UserConfig()
        self._cache: dict[str, User] = {}

    def get_user_by_id(self, user_id: str) -> Optional[User]:
        """Retrieve a user by their unique identifier."""
        if user_id in self._cache:
            return self._cache[user_id]

        user = self._repository.find_by_id(user_id)
        if user is not None:
            self._cache[user_id] = user
        return user
```

## Bad Examples
```python
# BAD: Inconsistent naming
class user_service:       # Should be PascalCase
    def GetUser(self):    # Should be snake_case
        myVar = 42        # Should be snake_case
        MAX = 100         # Constants at module level

# BAD: No whitespace conventions
x=1+2                     # Should be x = 1 + 2
def f( x , y ):           # No spaces after ( and before )
```

## Enforcement
- Format with Black or Ruff: `ruff format .`
- Lint with Ruff: `ruff check . --fix`
- Pre-commit hook: `ruff check && ruff format --check`
- CI: fail on any formatting violations