graycode_powerset.py

#!/usr/bin/env python
# encoding: utf-8

'''
This code is using binary shift and tricks to create powerset and also generator
'''

def powerset( l ):
	''' This code make a powerset list by using grey code'''
	# Anggaplah index item itu adalah binary
	d = dict(zip( 
	            (1<<i for i in range(len(l))), 
	            (set([e]) for e in l) 
	            )) 
	subset = set() 
	yield subset 
	for i in range(1, 1<<len(l)): 
		subset = subset ^ d[i & -i] 
		yield subset
		
if __name__ == '__main__':
	import sys
	
	if len(sys.argv) < 2:
		print ''' Usage: powerset <string> '''
		sys.exit(1)
	
	print list(powerset(sys.argv[1]))