Thanks castironpi and alex, for this:
def p(a,b):
if not b: return ['']
return [i+j for i in a for j in p(a,b-1)]
That is a thing of beauty! As usual you guys didn't disappoint.
(Validity check of alphabet removed; you didn't check for duplicate
characters.)
Here is the bloated mess I came up with. I did see that it had to be
recursive, and was proud of myself for getting it pretty much on the
first try, but the thing still reeks of my sorry old fortran-addled
mentality.
def validAlphabet(alphabet):
if not isinstance(alphabet,str):
return False
if len(alphabet) > 256:
return False
for index in range(len(alphabet)-1):
if not alphabet[index] < alphabet[index+1]:
return False
return True
def nextword(word,alphabet):
if len(word) == 1:
index = alphabet.find(word)
if index < 0:
raise ValueError("bad token found %s" % word)
if index == len(alphabet) -1:
return None
else:
return alphabet[index+1]
else:
a = nextword(word[1:],alphabet)
if a:
return word[0] + a
else:
b = nextword(word[0],alphabet)
if b:
return b + (len(word) - 1) * alphabet[0]
else:
return None
def allwords(length,alphabet="01"):
if not validAlphabet(alphabet):
raise ValueError("bad token list %s" % alphabet)
word = length * alphabet[0]
result = [word]
while word < length * alphabet[-1]:
word = nextword(word,alphabet))
result.append(word)
return result
######
if __name__ == "__main__":
for item in allwords(5,"abc"):
print item
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