# increment_binary_string.py

# increment_binary_string.py

def increment_binary(s):
   return '{:04b}'.format(1 + int(s, 2))

x = '0000'
for _ in xrange(16):
   print x
   x = increment_binary(x)

'0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111'