我有一个构建 Huffman 树的方法，如下所示：

def buildTree(tuples) :
    while len(tuples) > 1 :
        leastTwo = tuple(tuples[0:2])                  # get the 2 to combine
        theRest  = tuples[2:]                          # all the others
        combFreq = leastTwo[0][0] + leastTwo[1][0]     #enter code here the branch points freq
        tuples   = theRest + [(combFreq,leastTwo)]     # add branch point to the end
        tuples.sort()                                  # sort it into place
    return tuples[0]            # Return the single tree inside the list

但是当我用以下参数喂函数时：

[(1, 'b'), (1, 'd'), (1, 'g'), (2, 'c'), (2, 'f'), (3, 'a'), (5, 'e')]

我得到的错误为

  File "<stdin>", line 7, in buildTree
    tuples.sort()
TypeError: '<' not supported between instances of 'tuple' and 'str'

调试时，我发现错误是在tuples.sort()。