类的展现

class Prograne(object):
    def __init__(self,name,age):
        self.name=name
        if isinstance(age,int):
            self.age=age
        else:
            raise Exception("age must be int")
    def __str__(self):#重新写str方法
        return "%s is %s years old "%(self.name,self.age)

    def __dir__(self):#重新写dir方法
        return self.__dict__.keys()

if __name__=="__main__":
    p=Prograne("erfei",20)
    print(p)
    print(dir(p))