Python算法输出1-9数组形成的结果为100的所有运算式

from functools import reduce
operator = {
 1: '+',
 2: '-',
 0: ''
}
base = ['1', '2', '3', '4', '5', '6', '7', '8', '9']
def isHundred(num):
 #转化为8位3进制数，得到运算符数组
 arr = []
 for index in range(8):
  index = 7 - index
  arr.append(num // (3 ** index))
  num -= (num // (3 ** index)) * (3 ** index)
 arr = map(lambda x: operator[x], arr)
 #合并得到运算式
 formula = reduce(lambda x, y: x + y, zip(base, arr))
 formula = list(formula)
 formula.append('9')
 formula = ''.join(formula)
 #计算运算式结果
 res = eval(formula)
 return res, formula
if __name__ == '__main__':
 #所有可能的结果
 total = 3 ** 8
 for i in range(total):
  res, formula = isHundred(i)
  if res == 100:
   print(formula+' = 100')

/usr/bin/python3.5 /home/kang/workspace/Qt3d/test.py
123+45-67+8-9 = 100
123+4-5+67-89 = 100
123-45-67+89 = 100
123-4-5-6-7+8-9 = 100
12+3+4+5-6-7+89 = 100
12+3-4+5+67+8+9 = 100
12-3-4+5-6+7+89 = 100
1+23-4+56+7+8+9 = 100
1+23-4+5+6+78-9 = 100
1+2+34-5+67-8+9 = 100
1+2+3-4+5+6+78+9 = 100

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
l = []
for i in range(3):
 x = int(raw_input('integer:\n'))
 l.append(x)
l.sort()
print l

integer:
8
integer:
5
integer:
6
[5, 6, 8]