代码如下:

>>>def A():  
return A()  
>>>A() #无限循环，等消耗掉所有内存资源后，报最大递归深度的错误    
File "<pyshell#2>", line 2, in A return A()RuntimeError: maximum recursion depth exceeded  
class Bird:  
    def __init__(self):  
        self.hungry = True  
    def eat(self):  
        if self.hungry:  
            print "Ahaha..."  
            self.hungry = False  
        else:  
            print "No, Thanks!"  

该类定义鸟的基本功能吃，吃饱了就不再吃

输出结果:

代码如下:

>>> b = Bird()  
>>> b.eat()  
Ahaha...  
>>> b.eat()  
No, Thanks!  

下面一个子类SingBird,

代码如下:

class SingBird(Bird):  
    def __init__(self):  
        self.sound = 'squawk'  
    def sing(self):  
        print self.sound 

输出结果:

代码如下:

>>> s = SingBird()  
>>> s.sing()  
squawk  

SingBird是Bird的子类，但如果调用Bird类的eat()方法时,

代码如下:

>>> s.eat()  
Traceback (most recent call last):  
  File "<pyshell#5>", line 1, in <module>  
    s.eat()  
  File "D:\Learn\Python\Person.py", line 42, in eat  
    if self.hungry:  
AttributeError: SingBird instance has no attribute 'hungry'  

【错误分析】代码错误很清晰,SingBird中初始化代码被重写，但没有任何初始化hungry的代码

代码如下:

class SingBird(Bird):  
    def __init__(self):  
        self.sound = 'squawk'  
        self.hungry = Ture #加这么一句  
    def sing(self):  
        print self.sound