如何实现生成一个1-N位的字符串的列表

words_arr.py

class WordsArr(object):
    def __init__(self,col_count):
        self.total = 26**col_count

    def __getitem__(self,idx):
        if idx>self.total-1:
            raise IndexError("index out of range")
        nums = []
        lst = idx%26
        while idx/26:
            if (idx/26)>25:
                nums.append(25)
            else:
                nums.append(idx/26-1)
            idx=idx/26
        nums.append(lst)
        return "".join([chr(97+i) for i in nums])

    def __getslice__(self,start,end):
        for idx in xrange(start,end):
            yield self[idx]


if __name__ == "__main__":
    arr = WordsArr(5)
    for w in arr[23:200]:
        print w