Starting hamming database

hammingdb.py

#!/usr/bin/python3 -ttu

class hamming_db:
    def __init__(self, itemlen):
        self._itemlen = itemlen
        self._itemlist = []
        # List of dictionaries, containing entries from itemlist that match
        self._positiondb = [{} for _ in range(self._itemlen)]

    def add(self, item):
        if not len(item) == self._itemlen:
            raise RuntimeError('Item is the wrong length')
        self._itemlist.append(item)
        lastitemidx = len(self._itemlist)-1

        # Now add it to the index:
        for pos in range(self._itemlen):
            c = item[pos]
            posdict = self._positiondb[pos]
            if not c in posdict:
                posdict[c] = []
            posdict[c].append(lastitemidx)
            self._positiondb[pos] = posdict

def main():
    SIZE=4
    DB = hamming_db(SIZE)
    with open("/usr/share/dict/words", 'r') as words:
        for i, word in enumerate(words):
            if len(word) == SIZE:
                DB.add(word)
    print(DB._positiondb)

if __name__ == '__main__':
    main()