python类定义小问题

>>> class Athlete:
    def __init__ (self,a_name,a_dob=None,a_times=[]) :
        self.name = a_name
        self.dob = a_dob
        self.times = a_times

        
>>> sarah =Athlete('Sarah Sweeney','2002-6-27',['2.65','2:56','1.45'])
>>> james = Athlete('James Jone')

1、__init__     左右各是两个小短下划线_ _

2、 def (空格) __init__ (self) : 没有空格会提示语法错误。