Custom Sorting For Conlangs again

I've just revised that Python code I posted a while back for sorting lists of strings in customized alphabetical orders. I realized that it would be more efficient to implement it as a key function (which is evaluated once per item) rather than a cmp funtion (which is evaluated for each pair of items). Fortunately Python compares lists in a similar way to strings, thus making it possible.

 class CustomSorter(object):
    def __init__(self,alphabet):
        self.alphabet=alphabet

    def __call__(self,word):
        head,tail=self.separate(word1)
        key=[self.alphabet.index(head1)]
        if len(tail):
            key.extend(self(tail))
        return key

    def separate(self,word):
        candidates=self.Candidates(word)
        while candidates==[]:
            word=word[1:]
            candidates=self.Candidates(word)
        candidates.sort(key=len)
        head=candidates.pop()
        tail=word[len(head):]
        return head,tail

        def Candidates(self,word):
            return [letter for letter in self.alphabet if word.startswith(letter)]