Logarithmic integral exponent power implementation in Python

power.py

def power_linear(number, exponent):
    return sum([number * number for _ in range(exponent)])

def power_log(number, exponent):
    if exponent == 0:
        return 1

    half = power_log(number, exponent / 2)
    return half * half if exponent % 2 == 0 else number * half * half

print power_log(2, 4)

Stack overflow error because exponent never reaches 0. (Python 3 turns the int (1) to float (0.5))

exponent / 2 should be replaced with exponent>>1 in order to use as intended.