Generate sequence with unique 3-neighbourhood with no repetition

generoi-sarja.py

#!/usr/bin/env python

import random, itertools

def generate( symbols ):
	out = ""
	for s in symbols:
		out += s
	
	done = False

	while not done:
		found = False
		partial = out[-2:]

		for s in reversed(symbols):
				if s not in partial:
					candidate = partial + s
					
					is_ok = True
					for pc in itertools.permutations( candidate ):
						spc = "".join(pc)
						if spc in out:
							is_ok = False
					
					if is_ok:
						out += s
						found = True
						break
					

		if not found:
			done = True
	
	return out



result = generate("12345678")
print "result:", result
print "len:", len(result)

h = {}
for s in result:
	if s not in h:
		h[s] = 0
	h[s] += 1

print h

# output:
#
# result: 123456785638746827634853745284178
# len: 33
# {'1': 2, '3': 4, '2': 3, '5': 4, '4': 5, '7': 5, '6': 4, '8': 6}