1,由于Python是动态语言,任何实例在运行过程中,都可以动态地添加属性,python中通过slots 来限制添加属性。
如下代码:
class Student(objetc):
__slots__ = ('name', 'gender', 'score')
def __init__(self, name, gender, score):
self.name = name
self.gender = gender
self.score = score
>>> s = Student('Bob', 'male', 59)
>>> s.name = 'Tim' # OK
>>> s.score = 99 # OK
>>> s.grade = 'A'
Traceback (most recent call last):
...
AttributeError: 'Student' object has no attribute 'grade'
slots 的目的是限制当前类所拥有的属性。
对于继承类的限制属性添加如下:
class Person(object):
__slots__ = ('name', 'gender')
def __init__(self, name, gender):
self.name = name
self.gender = gender
class Student(Person):
__slots__ = ('score',)
def __init__(self, name, gender, score):
super(Student, self).__init__(name, gender)
self.score = score