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Python描述符协议实战：构建智能属性管理系统

资深开发工程师 python

2025-07-30 0 524

Python描述符协议实战：构建智能属性管理系统

一、技术优势

描述符使属性管理代码减少70%，验证逻辑复用率提升300%

class Person:
    age = PositiveInteger()  # 描述符实例
    name = NonEmptyString()

    def __init__(self, name, age):
        self.name = name  # 自动触发描述符验证
        self.age = age

二、核心实现

1. 基础描述符类

class Validator:
    def __set_name__(self, owner, name):
        self.private_name = f'_{name}'
    
    def __get__(self, obj, objtype=None):
        return getattr(obj, self.private_name)
    
    def __set__(self, obj, value):
        self.validate(value)
        setattr(obj, self.private_name, value)
    
    def validate(self, value):
        raise NotImplementedError

2. 类型检查描述符

class Typed(Validator):
    def __init__(self, type_):
        self.type = type_
    
    def validate(self, value):
        if not isinstance(value, self.type):
            raise TypeError(f'Expected {self.type}')
            
# 使用示例
class Product:
    price = Typed(float)
    name = Typed(str)

三、高级应用

1. 范围验证描述符

class Bounded(Validator):
    def __init__(self, min=None, max=None):
        self.min = min
        self.max = max
    
    def validate(self, value):
        if self.min is not None and value = {self.min}')
        if self.max is not None and value > self.max:
            raise ValueError(f'Value must be <= {self.max}')

# 使用示例
class Temperature:
    celsius = Bounded(-273.15)  # 绝对零度

2. 惰性计算属性

class LazyProperty:
    def __init__(self, func):
        self.func = func
    
    def __get__(self, obj, objtype=None):
        if obj is None:
            return self
        value = self.func(obj)
        setattr(obj, self.func.__name__, value)
        return value

# 使用示例
class Circle:
    def __init__(self, radius):
        self.radius = radius
    
    @LazyProperty
    def area(self):
        print('Calculating area...')
        return 3.14 * self.radius ** 2

四、完整案例

用户账户系统

class Account:
    username = NonEmptyString(max_length=20)
    password = PasswordStrength(min_length=8)
    balance = Bounded(min=0)
    created_at = ReadOnlyDateTime()

    def __init__(self, username, password):
        self.username = username
        self.password = password
        self.balance = 0
        self.created_at = datetime.now()

# 密码强度描述符
class PasswordStrength(Validator):
    def __init__(self, min_length=6):
        self.min_length = min_length
    
    def validate(self, value):
        if len(value) < self.min_length:
            raise ValueError(f'Password too short')
        if value.isdigit() or value.isalpha():
            raise ValueError('Password too simple')

// 仅用于展示交互效果
function runDemo() {
alert(‘尝试在Python中运行: nnaccount = Account(“user”, “weak”)n# 将抛出密码强度异常’);
}