Calculate the value of ‘a’ to the power ‘b’

Calculate the value of ‘a’ to the power ‘b’.
Test Data:
(power(3,4) -> 81
def power(a, b):
       if b == 0:
               return 1
       elif a == 0:
               return 0
       elif b == 1:
               return a
       else:
               return a * power(a, b - 1)

# test
print(power(3, 4))    # 81