Powers of two

"""Find the nearest power of 2 below and above an input number, along
with the diffs.
"""

import argparse
import math
import sys


def nearest_powers_of_two(num, output=True):
    """Find the powers of 2 nearest the input num, along with the diffs.
    If optional parameter output == True (the default), print the
    values as well as returning them. Return value is a list of tuples
    [(low, lowdiff), (high, highdiff)].
    """
    lg = math.floor(math.log2(num))
    lo = math.floor(math.pow(2, lg))
    hi = math.floor(math.pow(2, lg+1))
    lodiff = abs(lo-num)
    hidiff = abs(hi-num)
    lopower = round(math.log2(lo))
    hipower = round(math.log2(hi))
    if output:
        print(f'low power of two: {lo} (2**{lopower}), diff={lodiff}')
        print(f'high power of two: {hi} (2** {hipower}), diff={hidiff}')
    return [(lo, lodiff), (hi, hidiff)]


def main(argv):
    parser = argparse.ArgumentParser()
    parser.add_argument(
        'number',
        type=int,
        help='Number for which to find neighboring powers of 2.')
    args = parser.parse_args()
    nearest_powers_of_two(args.number)


if __name__ == "__main__":
    main(sys.argv)
    quit()