判断题：对于以下类定义： ```python class Student(): cls_teacher = 'Macdonald' cls_teacher = 'Linda' def __init__(self,name,age): self.name = name # 用于自我介绍的函数 def intro(self): print(f'My name is {self.name}.') ``` 以下代码能够正常运行 ``` a = Student('Alice',21) b = Student('Bob',20) b.nickname = a.nickname = "Ali" del a.nickname print(b.nickname) ```

错误。

因为在类定义中没有定义`nickname`属性，所以在给`a`和`b`对象分别赋值时会报错。如果要给`a`和`b`对象添加`nickname`属性，则需要在`__init__`方法中添加`self.nickname`属性的定义，如下：

class Student():
    cls_teacher = 'Macdonald'
    cls_teacher = 'Linda'
    def __init__(self,name,age):
        self.name = name 
        self.nickname = None # 添加nickname属性的定义
    # 用于自我介绍的函数
    def intro(self):
        print(f'My name is {self.name}.')

然后，以下代码才能正常运行：

a = Student('Alice',21)
b = Student('Bob',20)
b.nickname = a.nickname = "Ali"
del a.nickname
print(b.nickname) # 输出：Ali