python3 把该插入的位置找到保存到add_index中，然后遍历插入即可

while True:
    try:
        s = input()
        res = list(s)
        add_index = []
        for i in range(len(s)):
            if i == 0:
                if s[i].isdigit():
                    add_index.append(i)
                    continue
            elif not s[i].isdigit() and s[i-1].isdigit():
                add_index.append(i)
            elif s[i].isdigit() and not s[i-1].isdigit():
                add_index.append(i)
        for i in range(len(add_index)):
            res.insert(add_index[i]+i, '*')
        if res[-1].isdigit():
            res.append('*')
        print(''.join(res))
    except:
        break