class FirstClass:                   # 定义类对象
    def setData(self, value):        # 定义类方法
        self.data = http://www.mamicode.com/value           # self就指这个实例

    def display(self):
        print self.data             # self.data: 该实例的data值

# 实例化两个对象
x = FirstClass()
y = FirstClass()

x.setData("King Arthur")
y.setData(3.1415926)

x.display()
y.display()

# 直接修改data
x.data = "new value"
x.display()

class SubFirstClass(FirstClass):
    pass