Jan-24-2019, 07:57 AM
I have below code to test overload of the operator, add is tested ok, sub is not ok, after P1-p3, it becomes empty set, but my sub function is correct, anyone knows why? thanks
class Opera(object): def __init__(self,opera): self.opera=[] if type(opera) in (list,tuple): self.opera.extend(opera) def __add__(self, other): return Opera(self.opera+other.opera) def __sub__(self, other): return Opera(p for p in self.opera if p not in other.opera) def __str__(self): return 'Operator overload Example{}'.format(self.opera) p1=Opera(['red','Green','Orange']) p2=Opera(['go','stop']) p3=Opera(['Orange']) print ('p1:'+str(p1)) print ('p2:'+str(p2)) print ('p3:'+str(p3)) print ('p1+p2:'+str(p1+p2)) print ('p1-p3:'+str(p1-p3))