Somma numeri pari

def sumOfEven(lis,sum=0):
#@Somma solo i numeri pari della lista fornita in input
#@param lis : list (of integers)
#@return int (sum of even numbers of the list)
 if len(lis)==0:
  return 0
 elif len(lis)==1:
  if lis[0]%2==0:
   sum=sum+lis[0]
   return sum
  else:
   return sum
 else:
  if lis[0]%2==0:
   elem=lis[0]
   return sumOfEven(lis[1:],sum+elem)
  else:
   return sumOfEven(lis[1:],sum)