使用slots:

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使用__slots__:正常情况下,当我们定义了一个class,创建了一个class的实例后,我们可以给该实例绑定任何属性和方法,这就是动态语言的灵活性,先定义class:class Student(object):    def __init__(self, name, score):        self.name = name        self.score = score    def print_score(self):        print '%s: %s' % (self.name, self.score -2)然后,尝试给实例绑定一个属性:from   mycompany.web.Student import *s=Student('a','b')print s.names.name='Michael'print s.nameC:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/a2.pyaMichael还可以尝试给实例绑定一个方法:class Student(object):    def __init__(self, name, score):        self.name = name        self.score = score    def print_score(self):        print '%s: %s' % (self.name, self.score -2)    def set_age(self, age):  # 定义一个函数作为实例方法        self.age = ageclass Student(object):    def __init__(self, name, score):        self.name = name        self.score = score    def print_score(self):        print '%s: %s' % (self.name, self.score -2)    def set_age(self, age):        self.age = age        return self.agefrom   mycompany.web.Student import *s=Student('a','b')print s.names.name='Michael'print s.nameprint s.set_age(77)通常情况下,上面的set_score方法可以直接定义在class中,但动态绑定允许我们在程序运行的过程中动态给class加上功能,这在静态语言中很难实现。使用__slots__但是,如果我们想要限制class的属性怎么办？比如,只允许对Student实例添加name和age属性:为了达到限制的目的,Python允许在定义class的时候,定义一个特殊的__slots__变量,来限制该class能添加的属性:class Student(object):    def __init__(self, name,age, score):        self.name = name        self.age = age        self.score = score    def print_score(self):        print '%s: %s' % (self.name, self.score -2,self.score)-----------------------------------------------------------------------------class Student(object):    def __init__(self, name,age, score):        self.name = name        self.age = age        self.score = score    def print_score(self):        print '%s: %s' % (self.name, self.score -2,self.score)from   mycompany.web.Student import *s=Student('a',12,23)print s.names.name='Michael'print s.nameprint '---------------------------'print s.ages.age=34print s.ageprint '---------------------------'print s.scores.score=45print s.scoreC:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/a2.pyaMichael---------------------------1234---------------------------2345class Student(object):    __slots__ = ('name','age','score')    def __init__(self, name,age, score):        self.name = name        self.age = age        self.score = score    def print_score(self):        print '%s: %s' % (self.name, self.score -2,self.score)from   mycompany.web.Student import *s=Student('a',12,23)print s.nameC:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/a2.pya此时可以:
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