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当我们通过一个类创建了实例之后,仍然可以给实例添加属性,但是这些属性只属于这个实例。有些时候,我们可以需要限制类实例对象的属性,这时就要用到类中的_ _slots _ _ 属性了。_ _ slots_ _属性对于一个tuple,只有这个tuple中出现的属性可以被类实例使用。
class person(object):
__slots__ = ("name", "age","weight")
def __init__(self, name, age, weight):
self.name = name
self.age = age
self.weight = weight
Bruce = person("Bruce", 25,60)
print("%s is %d years old and he weights %s" %(Bruce.name, Bruce.age,Bruce.weight))
Bruce.tall = 180
person类实例化后,Bruce不能添加新的属性,_ _ slots_ _属性对于一个tuple属性赋值,只有这个tuple中出现的属性可以被类实例使用
- 使用_ _ slots _ _ 要注意, _ _ slots_ _定义的属性仅对当前类的实例起作用,对继承的子类实例是不起作用的,不会限制继承的子类实例化再添加新的属性
class human(object):
__slots__ = ("name", "age","weight")
class person(human):
#__slots__ = ("name", "age","weight")
def __init__(self, name, age, weight):
self.name = name
self.age = age
self.weight = weight
Bruce = person("Bruce", 25,60)
print("%s is %d years old and he weights %s" %(Bruce.name, Bruce.age,Bruce.weight))
Bruce.tall = 180
Bruce is 25 years old and he weights 60
- 如果子类本身也有_ _ slots_ _ 属性,子类的属性就是自身的 _ _ slots _ _ 加上父类的_ _ slots_ _
class human(object):
__slots__ = ("tall")
class person(human):
__slots__ = ("name", "age","weight")
def __init__(self, name, age, weight):
self.name = name
self.age = age
self.weight = weight
Bruce = person("Bruce", 25,60)
print("%s is %d years old and he weights %s" %(Bruce.name, Bruce.age,Bruce.weight))
Bruce.tall = 180
print("%s is %d years old and he weights %s and he\'s tall is %s" %(Bruce.name, Bruce.age,Bruce.weight,Bruce.tall))
Bruce.appearance = 'handsome'