Python计算不带括号的字符串

__author__ = ‘Alex‘
# -*- coding:UTF-8 -*-
import re
import string
str = "-10+30-20*11+40*21/5-100+70-2*13+14"
data_list=[]
sym_list=[]

data_list = re.findall(‘\d+‘,str)
sym_list = re.findall(‘\D+‘,str)

# print (data_list)
# print (sym_list)

def add (a1,a2,opr):
    if opr == ‘+‘:
        flag = False
        return a1+a2
def sub (a1,a2,opr):
    if opr == ‘-‘:
        flag = False
        return a1-a2
def mul(a1,a2,opr):
    if opr == ‘*‘:
        flag = True
        return a1*a2
def div(a1,a2,opr):
    if opr == ‘/‘:
        flag = True
        return a1/a2
if sym_list[0] == ‘-‘:
    data_list[0] = ‘-%s‘%(data_list[0])
    sym_list.remove(sym_list[0])
print (data_list)
print (sym_list)
while sym_list.count(‘*‘) != 0 or sym_list.count(‘/‘) != 0:
    for i in range(len(sym_list)):
        if sym_list[i] == ‘*‘:
            val = mul(float(data_list[i]),float(data_list[i+1]),‘*‘)
            data_list.remove(data_list[i])
            data_list.remove(data_list[i])
            data_list.insert(i,val)
            sym_list.remove(sym_list[i])
            break
        if sym_list[i] == ‘/‘:
            val = div(float(data_list[i]),float(data_list[i+1]),‘/‘)
            data_list.remove(data_list[i])
            data_list.remove(data_list[i])
            data_list.insert(i,val)
            sym_list.remove(sym_list[i])
            break
print (data_list)
print (sym_list)

while len(sym_list)>0:
    for i in range(len(sym_list)):
        if sym_list[i] == ‘+‘:
            val = add(float(data_list[i]),float(data_list[i+1]),‘+‘)
            data_list.remove(data_list[i])
            data_list.remove(data_list[i])
            data_list.insert(i,val)
            sym_list.remove(sym_list[i])
            break
        if sym_list[i] == ‘-‘:
            val = sub(float(data_list[i]),float(data_list[i+1]),‘-‘)
            data_list.remove(data_list[i])
            data_list.remove(data_list[i])
            data_list.insert(i,val)
            sym_list.remove(sym_list[i])
            break
print (data_list)
print (sym_list)