Python面试：类的特殊方法
【摘要】 1、call函数
class Foo(): def __init__(self): print("Foo-init") def __call__(self): print("Foo-call")
f = Foo()
f() # 重载了括号运算符
"""
Foo-init
Foo-call
"""12345678910111213
2、类装饰器
class De...
1、call函数
class Foo(): def __init__(self): print("Foo-init") def __call__(self): print("Foo-call")
f = Foo()
f() # 重载了括号运算符
"""
Foo-init
Foo-call
"""
2、类装饰器
class Decorator(): def __init__(self, func): print("Decorator-init") self.fun = func def __call__(self, args1, args2): print("Decorator-call") self.fun(args1, args2)
@Decorator
def add(a, b): print("a+b:", a+b)
# add(1, 2)
"""
Decorator-init
Decorator-call
a+b: 3
"""
3、new和init
class MyTuple(tuple): def __init__(self, seq): print("MyTuple-init") print("self:", self) # takes no parameters super(MyTuple, self).__init__() def __new__(cls, seq): print("MyTuple-new") # 过滤 g = [i for i in seq if isinstance(i ,int)] # 返回对象：self return super(MyTuple, cls).__new__(cls, g) t = MyTuple([1, 2, "-1"])
print(type(t), t)
"""
MyTuple-new
MyTuple-init
self: (1, 2)
<class '__main__.MyTuple'> (1, 2)
"""
4、set,get,delete
# 描述符 : 允许你自定义在引用一个对象属性时应该完成的事情
# __set__:在设计属性的时候被调用
# __get__:在读取属性的时候被调用
# __delete__:在删除属性的时候被调用
class Descriptor(): def __get__(self, instance, owner): print("get") def __set__(self, instance, value): print("set") def __delete__(self, instance): print("delete")
class A(): x = Descriptor()
a = A()
a.x
a.x = 1
del a.x
"""
get
set
delete
"""
5、描述符实例：属性做类型检查
class Attr(): def __init__(self, name, name_type): self.name = name self.name_type = name_type def __get__(self, instance, owner): return instance.__dict__[self.name] def __set__(self, instance, value): if not isinstance(value, self.name_type): raise TypeError("expected an {}".format(self.name_type)) instance.__dict__[self.name] = value def __delete__(self, instance): del instance.__dict__[self.name]
# p.name='jack' #名字必须是str
# p.age=18 #年龄必须是int
class Person(): name = Attr("name", str) age = Attr("age", int)
p=Person()
p.name= "Tom"
p.age = 123
参考：
文章来源: pengshiyu.blog.csdn.net，作者：彭世瑜，版权归原作者所有，如需转载，请联系作者。
原文链接：pengshiyu.blog.csdn.net/article/details/79607990
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