tentotwo.py

#!/usr/bin/env python3
"""
converts a power of ten to a power of two (or the reverse)
e.g. given x, 10^x = 2^y, solves for y
to convert 10^39 to a power of two: tentotwo.py 39
to convert 2^128 to a power of ten: tentotwo.py -r 128
https://tylerkerr.ca/b/2015/12/converting-powers-of-ten-to-powers-of-two
"""

import sys
from math import log

try:
    if sys.argv[1] == "-r":
        ptwo = int(sys.argv[2])
        pten = log(2 ** ptwo) / log(10)
        print("2 ^ %s   =   10 ^ %s   ≈  10 ^ %s" % (ptwo, pten, round(pten)))
    else:
        pten = int(sys.argv[1])
        ptwo = log(10 ** pten) / log(2)
        print("10 ^ %s   =   2 ^ %s   ≈  2 ^ %s" % (pten, ptwo, round(ptwo)))
    
except:
    print("usage: %s [-r] [exponent]" % sys.argv[0])