MRO顺序

class B():
    def __init__(self,b,*args,**kwargs):
        self.b = b
    def show(self):
        print(self.b)

class B1(B):
    def __init__(self,b,b1,*args,**kwargs):
        super(B1,self).__init__(b,*args,**kwargs)
        self.b1 = b1
    def show(self):
        print(self.b,self.b1)

class B2(B):
    def __init__(self,b,b2,*args,**kwargs):
        super(B2,self).__init__(b,*args,**kwargs)
        self.b2=b2
    def show(self):
        print(self.b,self.b2)

class D(B1,B2):
    def __init__(self, b ,b1,b2,d):
        super(D,self).__init__(b,b1,b2)
        self.d = d
    def show(self):
        print(self.b,self.b1,self.b2,self.d)

print(D.mro())
d = D(1,2,3,4)
d.show()