I once asked the fastest to calculate if a number was a power of two or not and I choked. Here is a nifty little way to do it.

poweroftwo.py

import sys

def isapoweroftwo(n):

  	if n == 0:
		return False

	if n & (n - 1) == 0:
		return True

	return False

if __name__ == "__main__":
	print isapoweroftwo(int(sys.argv[1]))