python - find largest power of two less than X number?

Question

I m doing this

def power_two(n, base = -1):
    result = 2 ** base
    if result < n:
        base += 1
        power_two(n, base)
    else:
        if result == n:
            print base
        else:
            print base - 1

what is the pythonic way to find largest power of two less than X number?

EDIT example: power_two(100) return only the power

Answer 1

Find the logarithm and truncate it:

def power_two(n):
    return int(math.log(n, 2))