python 类的装饰器
我们知道,在不改变原有代码的基础上,我们可以使用装饰器为函数添加新的功能。同理,一切皆对象,我们也可以使用装饰器为类添加类属性。what?
def deco(obj): obj.x = 1 obj.y = 2 return obj @deco # Foo = deco(Foo) class Foo: pass print(Foo.__dict__)
上述的代码为Foo属性字典添加了x和y属性,但如果想添加'name' = 'harden'呢,这需要更灵活的定义了。so
def deco(**kwargs): def wrapper(obj): for k, v in kwargs.items(): setattr(obj, k, v) return obj return wrapper @deco(x=1, y=2) class Foo: pass print(Foo.__dict__)
{'__module__': '__main__', '__dict__': <attribute '__dict__' of 'Foo' objects>, '__weakref__': <attribute '__weakref__' of 'Foo' objects>, '__doc__': None, 'x': 1, 'y': 2}
我们再定义类Bar,
@deco(name='curry') class Bar: pass
name属性也可以添加进去
再来个升级版,利用数据描述符和类的装饰器为类属性限定数据类型
我们知道,在不改变原有代码的基础上,我们可以使用装饰器为函数添加新的功能。同理,一切皆对象,我们也可以使用装饰器为类添加类属性。what? def deco(obj): obj.x = 1 obj.y = 2 return obj @deco # Foo = deco(Foo) class Foo: pass print(Foo.__dict__) 上述的代码为Foo属性字典添加了x和y属性,但如果想添加'name' = 'harden'呢,这需要更灵活的定义了。so def deco(**kwargs): def wrapper(obj): for k, v in kwargs.items(): setattr(obj, k, v) return obj return wrapper @deco(x=1, y=2) class Foo: pass print(Foo.__dict__) {'__module__': '__main__', '__dict__': <attribute '__dict__' of 'Foo' objects>, '__weakref__': <attribute '__weakref__' of 'Foo' objects>, '__doc__': None, 'x': 1, 'y': 2} 我们再定义类Bar, @deco(name='curry') class Bar: pass name属性也可以添加进去 再来个升级版,利用数据描述符和类的装饰器为类属性限定数据类型 #数据描述符,代理另一个新式类的属性 class Typedef: def __init__(self, key, expected_type): self.key = key self.expected_type = expected_type def __get__(self, instance, owner): # print('exec __get__') # print(instance) # print(owner) return instance.__dict__[self.key] def __set__(self, instance, value): # print('exec __set__') if not isinstance(value, self.expected_type): raise TypeError instance.__dict__[self.key] = value def __delete__(self, instance): instance.__dict__.pop(self.key) def deco(**kwargs): def wrapper(obj): for k, v in kwargs.items(): #为obj添加属性 如 name = Tpyedef('name', str) setattr(obj, k, Typedef(k, v)) return obj return wrapper @deco(name=str, age=int, salary=float) # =====》People= wrapper(People) class People: def __init__(self, name, age, salary): self.name = name self.age = age self.salary = salary p1 = People('handen', 18, 111.11) print(p1.name) print(p1.__dict__)