递归函数使a ^ b

Question

My recursive function doesn't seem to be working - it's supposed to take parameters a and b and return a^b .

Here it is:

def power(a, b):
       If b == 0:
               return
       return a * power(a,  b-1)
power(2,  3)

Answer 1

Base case return statement is null. You should return 1 (since a^0 = 1 for a != 0 ).

if b == 0:
    return 1

You might want to handle the case for a = 0 separately though, since 0^0 is mathematically undefined:

if a == 0:
    if b > 0:
        return 0
    else
        # raise an exception here?

Answer 2

def power(a, b):
   if b == 0:
      return 1;
   return a * power(a,  b - 1);