众所周知，python是一门弱类型的语言，变量可以随意赋值成任意类型，但是通过描述符，我们可以把数据变成强类型的。
我们为数据设置数据描述符，因为数据描述的优先级大于实例属性，所以在给数据赋值的时候会优先出发数据描述符。
普通版
class Typed:
def __init__(self, name, expected_type):
self.name = name
self.expected_type = expected_type def __get__(self, instance, owner):
if instance is None:
return self # 如果实例化用People.name调用的话，就返回Typed的实例name
return instance.__dict__[self.name] def __set__(self, instance, value):
if not isinstance(value, self.expected_type):
raise TypeError('Type error')
instance.__dict__[self.name] = value def __delete__(self, instance):
instance.__dict__.pop(self.name) class People:
name = Typed('name', str)
age = Typed('age', int)
salary = Typed('salary', float) def __init__(self, name, age, salary):
self.name = name
self.age = age
self.salary = salary # p1 = People(123, 18, 3333.3) # TypeError: Type error
# p1=People('egon','18',3333.3) # TypeError: Type error
# p1=People('egon',18,3333) # TypeError: Type error p1 = People('egon', 18, 3333.33) # 正确
用类的装饰器实现
先回顾一下setattr的语法
语法
setattr() 语法：
setattr(object, name, value)
参数
- object -- 对象。
- name -- 字符串，对象属性。
- value -- 属性值。
class Typed:
def __init__(self, name, expected_type):
self.name = name
self.expected_type = expected_type def __get__(self, instance, owner):
if instance is None:
return self
return instance.__dict__[self.name] def __set__(self, instance, value):
if not isinstance(value, self.expected_type):
raise TypeError('type error')
instance.__dict__[self.name] = value def __delete__(self, instance):
self.__dict__.pop(self.name) def typeassert(**kwargs):
def decorator(cls):
for name, expected_type in kwargs.items():
setattr(cls, name, Typed(name, expected_type))
return cls return decorator @typeassert(name=str, age=int, salary=float)
class People:
def __init__(self, name, age, salary):
self.name = name
self.age = age
self.salary = salary p1 = People('edward', 18, 30000.00)