题解 | #字符统计#

while True:
    try:
        dic = {}
        k = input()
        for i in k:
            if i in dic.keys():
                dic[i] += 1
            else:
                dic[i] = 1
        # lambda 里-x[1]是dic.values()逆序，x[0]是dic.keys()正序
        dic = dict(sorted(dic.items(),key=lambda x : (-x[1], x[0])))
        print("".join(dic.keys()))
    except:
        break

重点在于用lambda函数进行双重排序：

lambda 里-x[1]是dic.values()逆序，x[0]是dic.keys()正序