首先，我也不知道是不是python 中有类变量这个东西，不过叫不叫这个不重要，不过是一个文字游戏，关键是它的行为是什么。

代码如下

class One:
    def __init__(self):
        self.one = 1
        self.two = 2

    def printnum(self, num):
        if num == 1:
            print(self.one)
        elif num == 2:
            print(self.two)
class test:
    one=One()
    def __init__(self,num):
        self.one.printnum(num)

if __name__ == "__main__":
    t = test(1)

上面的代码直接打印出来 1

不叫self 调用

class One:
    def __init__(self):
        self.one = 1
        self.two = 2

    def printnum(self, num):
        if num == 1:
            print(self.one)
        elif num == 2:
            print(self.two)



class test:
    one=One()
    def __init__(self,num):
        self.one.printnum(num)


    def print2(self,num):
       	one.printnum(num)


if __name__ == "__main__":
    t = test(1)
    t.print2(1)

然而直接报错

在方法中，重新使用个名字 `self.tow`去调用

代码如下

class One:
    def __init__(self):
        self.one = 1
        self.two = 2

    def printnum(self, num):
        if num == 1:
            print(self.one)
        elif num == 2:
            print(self.two)



class test:
    one=One()
    def __init__(self,num):
        self.one.printnum(num)


    def print2(self,num):

        self.two.printnum(num)



if __name__ == "__main__":
    t = test(1)
    t.print2(1)

直接报错

在test类中，直接修改One 中属性值，查看是否会改变

代码如下

class One:
    def __init__(self):
        self.one = 1
        self.two = 2

    def printnum(self, num):
        if num == 1:
            print(self.one)
        elif num == 2:
            print(self.two)



class test:
    one=One()
    def __init__(self,num):
        self.one.printnum(num)


    def print2(self,num):
        self.one.one =2
        self.one.printnum(num)


if __name__ == "__main__":
    t = test(1)
    t.print2(1)

打印出来 1 2 ，修改成功

那再次新建一个test的实例，查看修改是否能在两个test实例访问

代码如下

class One:
    def __init__(self):
        self.one = 1
        self.two = 2

    def printnum(self, num):
        if num == 1:
            print(self.one)
        elif num == 2:
            print(self.two)



class test:
    one=One()
    def __init__(self,num):
        self.one.printnum(num)


    def print2(self,num):
        self.one.one =2
        self.one.printnum(num)


if __name__ == "__main__":
    t = test(1)
    t.print2(1)

    t2 = test(1)

结果是的，可以在两个不同的实例之间访问

新建一个新的类，也包含一个python中的类变量，查看修改能够访问

代码如下

class One:
    def __init__(self):
        self.one = 1
        self.two = 2

    def printnum(self, num):
        if num == 1:
            print(self.one)
        elif num == 2:
            print(self.two)



class test:
    one=One()
    def __init__(self,num):
        self.one.printnum(num)


    def print2(self,num):
        self.one.one =2
        self.one.printnum(num)

class test2:

    one=One()
    def __init__(self,num):
        self.one.printnum(num)


    def print2(self,num):
        self.one.one =2
        self.one.printnum(num)


if __name__ == "__main__":
    t = test(1)
    t.print2(1)

    t2 = test(1)


    t3 = test2(1)