python-patterns

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# Python 开发模式

用于构建健壮、高效和可维护应用程序的惯用 Python 模式与最佳实践。

## 何时激活

* 编写新的 Python 代码
* 审查 Python 代码
* 重构现有的 Python 代码
* 设计 Python 包/模块

## 核心原则

### 1. 可读性很重要

Python 优先考虑可读性。代码应该清晰且易于理解。

```python
# Good: Clear and readable
def get_active_users(users: list[User]) -> list[User]:
    """Return only active users from the provided list."""
    return [user for user in users if user.is_active]


# Bad: Clever but confusing
def get_active_users(u):
    return [x for x in u if x.a]
```

### 2. 显式优于隐式

避免魔法；清晰说明你的代码在做什么。

```python
# Good: Explicit configuration
import logging

logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)

# Bad: Hidden side effects
import some_module
some_module.setup()  # What does this do?
```

### 3. EAFP - 请求宽恕比请求许可更容易

Python 倾向于使用异常处理而非检查条件。

```python
# Good: EAFP style
def get_value(dictionary: dict, key: str) -> Any:
    try:
        return dictionary[key]
    except KeyError:
        return default_value

# Bad: LBYL (Look Before You Leap) style
def get_value(dictionary: dict, key: str) -> Any:
    if key in dictionary:
        return dictionary[key]
    else:
        return default_value
```

## 类型提示

### 基本类型注解

```python
from typing import Optional, List, Dict, Any

def process_user(
    user_id: str,
    data: Dict[str, Any],
    active: bool = True
) -> Optional[User]:
    """Process a user and return the updated User or None."""
    if not active:
        return None
    return User(user_id, data)
```

### 现代类型提示（Python 3.9+）

```python
# Python 3.9+ - Use built-in types
def process_items(items: list[str]) -> dict[str, int]:
    return {item: len(item) for item in items}

# Python 3.8 and earlier - Use typing module
from typing import List, Dict

def process_items(items: List[str]) -> Dict[str, int]:
    return {item: len(item) for item in items}
```

### 类型别名和 TypeVar

```python
from typing import TypeVar, Union

# Type alias for complex types
JSON = Union[dict[str, Any], list[Any], str, int, float, bool, None]

def parse_json(data: str) -> JSON:
    return json.loads(data)

# Generic types
T = TypeVar('T')

def first(items: list[T]) -> T | None:
    """Return the first item or None if list is empty."""
    return items[0] if items else None
```

### 基于协议的鸭子类型

From Luohaothu/everything-codex, MIT.

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