计算器开发需求

1. 实现加减乘除及拓号优先级解析
2. 用户输入 1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )等类似公式后，必须自己解析里面的(),+,-,*,/符号和公式，运算后得出结果，结果必须与真实的计算器所得出的结果一致

#coding=utf-8
import redef sub_calc(formula):""" 计算一个加减乘除表达式的值"""flag = Truewhile flag:m = re.search('\d+\.?\d*[*/]-?\d+\.?\d*',formula) #先匹配乘除  举例： 5.12 * -123.12 ,  - 5.12 / -123.12if m:sub_mul_div = m.group()res = calc_multi_divd(sub_mul_div)formula = formula.replace(sub_mul_div,res)  # 将乘除表达式的结果替换，循环判断是否还有乘除表达式print "*" * 10,"乘除表达式:",formulaelse:print "*" * 10 ,"乘除计算完毕"flag = Falseprint "*" * 10,"子括号里面计算乘除后的表达式 ",formula result = calc_add_stract(formula) #计算加减法return result
def calc_multi_divd(formula):"""计算单个的乘除法表达式"""print "*" * 20,"单个的乘除法表达式",formulaf_list = re.split('[*/]',formula)print "*" * 20 ,"单个的乘除表达式列表",f_listif '*' in formula:res = float(f_list[0]) * float(f_list[1])elif '/' in formula:res = float(f_list[0]) / float(f_list[1])return str(res)
def calc_add_stract(formula):"""计算加减法，通过reduce 两两计算"""print "*" * 20,"没有处理正负号的加减表达式: ",formula#对符号进行处理formula = formula.replace('--','+')formula = formula.replace('++','+')formula = formula.replace('-+','-')formula = formula.replace('+-','-')print "*" * 20 ,"处理完正负号的加减表达式：",formula#对一个加减表达式，-变成+-，为了进行split成列表用于reduce计算formula = formula.replace('-','+-')formula_list = formula.split('+')print "*" * 20,"按加号分割的列表：",formula_list   #第一个数为负数，则列表第一个字段为空if formula_list[0] == '':formula_list = formula_list[1:]"""result = 0for i in formula_list:if '-' in i: stract_list = i.split('-')result = float(stract_list[0]) - float(stract_list[1]) + resultelse:result += float(i) """result = reduce(lambda x,y: float(x) + float(y),formula_list)print "*" * 20 ,"加减表达式的结果:" ,resultreturn str(result)
def calc(formula):flag = Truewhile flag:m = re.search('\([^()]*\)',formula)if m:print "*" * 5, "计算匹配到的括号表达式：",m.group()sub_formula = m.group().strip('()')res = sub_calc(sub_formula)      #先计算括号内的表达式formula = formula.replace(m.group(),res)  #将表达式计算出来的结果替换原括号，再一次循环判断是否还有括号else:flag = False print "*" * 5,"最终的去括号后的表达式:", formularesult = sub_calc(formula)return result        if __name__ == '__main__':formula = "1 - 2 * ( (60-30 +(-9-2-5-2*3-5/3-40*4/2-3/5+6*3) * (-9-2-5-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )"print "要计算的表达式:", formula #去掉所有的空格formula = re.sub('\s','',formula)print "去掉空格后的表达式",formulares = calc(formula)print "最终的结果:",res