python入门 实现计算器功能

# Author：Wang Zhuoqun
#实现计算器

import re,json

stra = "1-2*((60-30+(-40/5)*(9-2*5/3+7/3*99/4*2998+10*568/14))-(-4*3)/(16-3*2))"

def con(stra):
    """
    将其转化为可用格式
    """
    strb = re.sub("-", "+-", stra)
    strb = re.sub("/", "*/", strb)
    return strb

def MUL(str1):
    """
    实现功能乘除
    """
    mul0 = 1.0
    list_mul = re.split("\*", str1)
    for i in range(len(list_mul)):
        if "/" in list_mul[i]:
            list_mul[i] = list_mul[i].strip("/")
            list_mul[i] = str(1 / float(list_mul[i]))
        else:
            pass
    for i in list_mul:
        i = float(i)
        mul0 = mul0 * i
    mul0 = str(mul0)
    return mul0

def add(str1):
    """
    实现功能加减
    """
    add0 = 0.0
    list_add = re.split("\+", str1)
    for i in list_add:
        if i == "":
            pass
        else:
            i = float(i)
            add0 = add0 + i
    add0 = str(add0)
    return add0

strc = con(stra)

n = 1
while n>0:
    strb = strc
    if "(" in strc:
        m = 1
        while m >0:
            if "(" in strb:
                str1 = re.search("\(.+\)", strb).group()
                str1 = str1[1:]
                strb = str1
            else:
                m = 0

        str2 = re.search("\).+", str1)
        if str2 == None:
            str1 = str1.strip(")")
        else:
            str2 = str2.group()
            str1 = str1.replace(str2, '')
        str3 = str1

        if "--" in str1:
            str1 = str1.replace("--", "")
        else:
            pass
        if "*" in str1:
            list1 = re.split("\+", str1)
            for j in list1:
                if "*" in j :
                    j1 = MUL(j)
                    str1 = str1.replace(j,j1)
                else:
                    pass
        else:
            pass
        if "+" in str1:
            j1 = add(str1)
            str3 = "("+ str3 +")"
            strc = strc.replace(str3,j1)
        else:
            pass
    else:
        if "*" in strc:
            list1 = re.split("\+", strc)
            for j in list1:
                if "*" in j :
                    j1 = MUL(j)
                    strc = strc.replace(j,j1)
                else:
                    pass
        else:
            pass
        if "+" in strc:
            j1 = add(strc)
            strc = strc.replace(strc,j1)
            print(strc)
        else:
            pass
        n = 0