python实现两个数乘积

def a (x , y):
b = x * y
if b % 3 ==0:
return b
else:
return None
l = a (3,4)
print(l)
两位数的乘积不是3倍则返回None 请问有几种写法

 def a (x , y):
   b=x*y
   return (b if(b%3==0) else None)

def a (x , y):
  b = x * y
  if b % 3 ==0:
    return b
  return None