python类属性设置默认值

class Cat():
    def __init__(self, name, color):
        self.name = name
        self.color = color
        self.age = 3
 
    def eat(self):
        print('cat ' + self.name + ' color ' + self.color + ', now eat')
 
    def run(self):
        print('cat ' + self.name + ' color ' + self.color + ', now run')
 
    def print_age(self):
        print('cat`s age is ' + str(self.age))