python3的私有属性和继承

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写在最前面：从最简单讲起

先看一个最简单的类的例子

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s):
        self.name = n
        self.age = a
        self.sex = s
        self.__weight = w

    def infomation(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))


if __name__ == '__main__':
    # 实例化类
    p = people('Mike', 25, 60, 'man')
    p.infomation()

简单的不能再简单了

Mike is a 25 yesrs old man and weights 60kg

当我试图在类外直接访问私有属性

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s):
        self.name = n
        self.age = a
        self.sex = s
        self.__weight = w

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))


if __name__ == '__main__':
    # 实例化类
    p = people('Mike', 25, 60, 'man')
    print(p.__weight)

 会报错

AttributeError: 'people' object has no attribute '__weight'

说明weight作为私有属性，不能直接访问

那有没有可能绕过去呢，可以

为了方便描述，我们给prople类再加一个私有属性height并赋值180，然后我们试图访问__height

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s):
        self.name = n
        self.age = a
        self.sex = s
        self.__weight = w
        self.__height = 180

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))



class Programmer(people):
    language = ''

    def __init__(self,n, a, w, s, l):
        # 调用父类的构函
        people.__init__(self, n, a, w, s)
        self.language = l
        # 重写父类的方法

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg.He uses %d" % (self.name, self.age, self.sex, self.__weight,self.language))


if __name__ == '__main__':
    # 实例化类
    p = people('Mike', 25, 60, 'man')
    print(p.__height)

AttributeError: 'people' object has no attribute '__height'

很显然，不可以

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s):
        self.name = n
        self.age = a
        self.sex = s
        self.__weight = w
        self.__height = 180

if __name__ == '__main__':
    # 实例化类
    p = people('Mike', 25, 60, 'man')
    print(p._people__height)

诶，这样就可以了

180

 然后我们创造一个Programmer来继承这个类的所有属性，包括私有属性然后又加了一个language的非私有属性

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s):
        self.name = n
        self.age = a
        self.sex = s
        self.__weight = w
        self.__height = 180

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))



class Programmer(people):
    language = ''

    def __init__(self,n, a, w, s, l):
        # 调用父类的构函
        people.__init__(self, n, a, w, s)
        self.language = l
        # 重写父类的方法

    def information(self):
        print("%s is a %d yesrs old %s and weights %dkg.He uses %s" % (self.name, self.age, self.sex, self.__weight,self.language))


if __name__ == '__main__':
    # 实例化类
    p = people('Mike', 25, 60, 'man')
    print(p._people__weight)
    q = Programmer('Mike', 25, 60, 'man', 'python')
    p.information()
    q.information()

运行，我们会发现报错

AttributeError: 'Programmer' object has no attribute '_Programmer__weight'

如果要访问，应该是这样

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s):
        self.name = n
        self.age = a
        self.sex = s
        self.__weight = w
        self.__height = 180

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))



class Programmer(people):
    language = ''

    def __init__(self,n, a, w, s, l):
        # 调用父类的构函
        people.__init__(self, n, a, w, s)
        self.language = l
        # 重写父类的方法

    def information(self):
        print("%s is a %d yesrs old %s and weights %dkg.He uses %s" % (self.name, self.age, self.sex, self._people__weight,self.language))


if __name__ == '__main__':
    # 实例化类
    p = people('Mike', 25, 60, 'man')
    print(p._people__weight)
    q = Programmer('Mike', 25, 60, 'man', 'python')
    p.information()
    q.information()

Mike is a 25 yesrs old man and weights 60kg
Mike is a 25 yesrs old man and weights 60kg.He uses python

如果我们访问非私有属性

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s):
        self.name = n
        self.age = a
        self.sex = s
        self.__weight = w
        self.__height = 180

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))



class Programmer(people):
    language = ''

    def __init__(self,n, a, w, s, l):
        # 调用父类的构函
        people.__init__(self, n, a, w, s)
        self.language = l
        # 重写父类的方法

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg.He uses %d" % (self.name, self.age, self.sex, self.__weight,self.language))


if __name__ == '__main__':
    # 实例化类
    p = people('Mike', 25, 60, 'man')
    print(p._people__weight)
    q = Programmer('Mike', 25, 60, 'man', 'python')
    p.information()
    #print(q._Programmer__height)
    print(q.name)

自然是可以的

60
Mike is a 25 yesrs old man and weights 60kg
Mike

如果我们不继承weight

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s):
        self.name = n
        self.age = a
        self.sex = s
        self.__weight = w
        self.__height = 180

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))



class Programmer(people):
    language = ''

    def __init__(self,n, a, s, l):
        # 调用父类的构函
        people.__init__(self, n, a, s, l)
        self.language = l
        # 重写父类的方法

    def information(self):
        print("%s is a %d yesrs old %s and he uses %s" % (self.name, self.age, self.sex,self.language))


if __name__ == '__main__':
    # 实例化类
    p = people('Mike', 25, 60, 'man')
    print(p._people__weight)
    q = Programmer('Mike', 25, 'man', 'python')
    p.information()
    #print(q._Programmer__height)
    print(q.name)
    q.information()

60
Mike is a 25 yesrs old man and weights 60kg
Mike
Mike is a 25 yesrs old python and he uses python

对于私有属性，我们虽然继承了，但是可以用不上

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s, h):
        self.name = n
        self.age = a
        self.__weight = w
        self.sex = s
        self.height = h

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))
        print(self.sex)


class Programmer(people):

    language = ''

    def __init__(self, n, a, w, s, h, l):
        # 调用父类的构函
        people.__init__(self, n, a, w, s, h)
        self.language = l
        # 重写父类的方法

    def information(self):
        print("%s is a %d yesrs old %s and he is %d tall and he uses %s" % (self.name, self.age, self.sex,self.height,self.language))



if __name__ == '__main__':
    # 实例化类
    q = Programmer('Mike',25,60,'man',170,'python')
    q.information()

Mike is a 25 yesrs old man and he is 170 tall and he uses python

可以看到，虽然我们继承了weight，参数也给了weight，但是我们并没有用到，如果想要访问weight这个私有属性呢

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s, h):
        self.name = n
        self.age = a
        self.__weight = w
        self.sex = s
        self.height = h

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))
        print(self.sex)


class Programmer(people):

    language = ''

    def __init__(self, n, a, w, s, h,l):
        # 调用父类的构函
        people.__init__(self, n, a, w, s, h)
        self.language = l
        # 重写父类的方法

    def information(self):
        print("%s is a %d yesrs old %s and he is %d tall and he uses %s,weights %dkg" % (self.name, self.age, self.sex,self.height,self.language,self._people__weight))



if __name__ == '__main__':
    # 实例化类
    q = Programmer('Mike',25,60,'man',170,'python')
    q.information()

然后可以看到

Mike is a 25 yesrs old man and he is 170 tall and he uses python,weights 60kg

如果我们想直接通过子类访问父类的私有属性呢？也可以

class people:

    name = ''     # 定义基本属性
    age = 0
    sex = ''
    __weight = 0  # 定义私有属性,私有属性在类外部无法直接进行访问

    # 定义构造方法
    def __init__(self, n, a, w ,s, h):
        self.name = n
        self.age = a
        self.__weight = w
        self.sex = s
        self.height = h

    def information(self):
        print("%s is a %d yesrs old %s and weights %skg" % (self.name, self.age, self.sex, self.__weight))
        print(self.sex)


class Programmer(people):

    language = ''

    def __init__(self, n, a, w, s, h,l):
        # 调用父类的构函
        people.__init__(self, n, a, w, s, h)
        self.language = l
        # 重写父类的方法

    def information(self):
        print("%s is a %d yesrs old %s and he is %d tall and he uses %s,weights %dkg" % (self.name, self.age, self.sex,self.height,self.language,self._people__weight))



if __name__ == '__main__':
    # 实例化类
    q = Programmer('Mike',25,60,'man',170,'python')
    q.information()
    print(q._people__weight)

Mike is a 25 yesrs old man and he is 170 tall and he uses python,weights 60kg
60

再来看一个例子，是我看到某位博主的贴一下他的代码

class Person(object):
    # 构造函数
    def __init__(self, name):
        self.name = name
        self.__age = 18

obj = Person("lily")
print(obj.name)

class Student(Person):
    def __init__(self):
        self.__gender = 'male'
 
stu = Student()
print(stu._Student__gender)
print(stu._Person__age)

这里他当然无法访问age，因为没有继承父类的构造函数，应该像这样

class Person(object):
    # 构造函数
    def __init__(self, name):
        self.name = name
        self.__age = 18


obj = Person("lily")
print(obj.name)


class Student(Person):
    def __init__(self,name):
        Person.__init__(self,name)
        self.__gender = 'male'


stu = Student('lily')
print(stu._Student__gender)
print(stu.name)
print(stu._Person__age)

这个很容易使人产生困惑，今天差点没把我绕死，以上的例子都是很经典的，我精心设计的，希望大家能学到一点东西

本来是想写类的继承的，写到私有属性上去了。。。

做学问呢要严谨，一丝不苟，我会对我的每一行代码负责，绝不复制粘贴，用心给大家讲解