计算器

import re
def cal_mini_exp(mini):
    # ‘40/5‘  ‘2*5‘
    if ‘*‘ in mini:
        num1,num2 = mini.split(‘*‘)
        return str(float(num1)*float(num2))
    elif ‘/‘ in mini:
        num1, num2 = mini.split(‘/‘)
        return str(float(num1) / float(num2))

def dealwith(exp):
    exp = exp.replace(‘--‘,‘+‘)
    exp = exp.replace(‘+-‘,‘-‘)
    exp = exp.replace(‘-+‘,‘-‘)
    exp = exp.replace(‘++‘,‘+‘)
    return exp

def calculate(son_exp):
    ‘‘‘
    计算没有括号的表达式的结果  (9-2*5/3+7/3*99/4*2998+10*568/14)
    ‘‘‘
    son_exp = son_exp.strip(‘()‘)
    while True:  # ‘完成了一个表达式中所有乘除法的计算‘
        ret = re.search(‘\d+\.?\d*[*/]-?\d+\.?\d*‘,son_exp)  #(9-3.33333+7/3*99/4*2998+10*568/14)
        if ret:
            mini_exp = ret.group()    #2*5 10/3
            res = cal_mini_exp(mini_exp)  # 2*5 3.33333
            son_exp = son_exp.replace(mini_exp,res,1)  #(9-3.33333+7/3*99/4*2998+10*568/14)
        else:break
    son_exp = dealwith(son_exp)   # 整理表达式中的符号
    ret_l = re.findall(‘[+-]?\d+\.?\d*‘,son_exp)
    sum = 0
    for i in ret_l:
        sum += float(i)
    return str(sum)

def remove_bracket(express):
    while True:
        ret = re.search(‘\([^()]+\)‘, express)  # 是否匹配上的对象
        if ret:
            son_exp = ret.group()  # 子表达式 (-40/5)
            # 计算 计算乘除法 再计算加减法
            ret = calculate(son_exp)  # -8
            express = express.replace(son_exp, ret, 1)
        else:
            break
    return express

def main(express):
    express = express.replace(‘ ‘,‘‘)
    express = remove_bracket(express)
    ret = calculate(express)
    print(ret)

if __name__ == ‘__main__‘:
    express = "-1 + 2 * ((60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )"
    main(express)