1.__str__
首先介绍__str__
class Students(object): def __init__(self, *args): self.names = args
# def __str__(self): # return str(self.names) # __repr__ = __str__ ss = Students('hyq','ysy') ss >>><__main__.Students at 0x2075a779828>
打印类对象显示的是对象的内存地址,下面重构__repr__和__str__方法
再看:
class Students(object): def __init__(self, *args): self.names = argsdef __str__(self): return str(self.names) # def __repr__(self): # return str(self.names) ss = Students('hyq','ysy') ss >>><__main__.Students at 0x2075a78a860>
class Students(object): def __init__(self, *args): self.names = args
# def __str__(self): # return str(self.names) def __repr__(self): return str(self.names) ss = Students('hyq','ysy') ss >>>('hyq', 'ysy')
可以看到,重构__repr__方法后,直接输出对象,能够按照__repr__中定义的格式进行显示;
而重构__str__方法后,直接输出对象,显示的是对象的内存地址,并不是__str__定义的格式
当然,用print都能够显示__repr__和__str__定义的格式
class Students(object): def __init__(self, *args): self.names = args
# def __str__(self): # return str(self.names) def __repr__(self): return str(self.names) ss = Students('hyq','ysy') print(ss) >>>('hyq','ysy') ————————————————————————————————————————————分割线———————————————————————————————————— class Students(object): def __init__(self, *args): self.names = argsdef __str__(self): return str(self.names) # def __repr__(self): # return str(self.names) ss = Students('hyq','ysy') print(ss) >>>('hyq','ysy')
注意:
在代码中一般写成:
def __str__(self): return str(self.names) __repr__ = __str__
2.__len__
如果一个类表现得像一个list,要获取有多少元素,就得用len()函数
要让len()函数正常工作,类必须提供一个特殊方法__len__(),返回元素的个数
class Students(object): def __init__(self, *args): self.names = args def __len__(self): return len(self.names) ss = Students('hyq','ysy') print(len(ss) >>>2