实例属性的增删改查

class Chinese:
    def __init__(self, name):
        self.name = name

    def play_ball(self):
        print('%s 正在打篮球' % self.name)


p1 = Chinese('小白')
p1.age = 19    # 实例只有数据属性，没有函数属性
print(p1.__dict__)
del p1.age
print(p1.__dict__)
输出：
{'name': '小白', 'age': 19}
{'name': '小白'}

class MyData:
    pass
x = 1
y = 2
MyData.x = 1
MyData.y = 2
p1 = MyData()
print(p1.x)
输出：
1

class Chinese:
    country = 'china'
    def __init__(self, name):
        self.name = name

    def play_ball(self):
        print('%s 正在打篮球' % self.name)


p1 = Chinese('alex')
p1.country = 'japan'
print(p1.country)
print(Chinese.country)
输出：
japan
china