python计算器作业

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

#找到最内层的括号，
#处理括号内的符号变换
#先乘除
# 后加减
import re
a='1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )'

def brcket(num):
    '''去括号'''
    regax=re.search('\([^()]+\)',num)
    regax=regax.group()
    return regax

def change_char(num):
    '''++=+ +-=- --=+ -+=-'''
    if '++' in num:
        num=num.replace('++','+')
        return num
    elif '+-' in num:
        num=num.replace('+-','-')
        return num
    elif '--' in num :
        num=num.replace('--','+')
        return num
    elif '-+' in num:
        num=num.replace('-+','-')
        return num
    else:return num

def multi_div(num):
    '''先算乘除'''
    num=change_char(num)
    regax=re.search('[\-]?\d+(\.\d+)?[*/]+[-]?\d+(\.\d+)?',num)
    regax=regax.group()
    if '*' in regax:
        a,b=regax.strip().split('*')
        num=num.replace(regax,'+'+str(float(a)*float(b)))
        return num
    if '/' in regax:
        a,b=regax.strip().split('/')
        num=num.replace(regax,'+'+str(float(a)/float(b)))
        return num

def add_min(num):
    '''再算加减'''
    num=change_char(num)
    regax=re.search('[+-]?\d+(\.\d+)?[+\-]+\d+(\.\d+)?',num)
    regax=regax.group()
    if '+' in regax:
        a,b=regax.strip().split('+')
        num=num.replace(regax,str(float(a)+float(b)))
        return num
    if '-' in regax:
        a,b=regax.strip().split('-')
        num=num.replace(regax,str(float(a)-float(b)))
        return num

#第一层括号
num_org='1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )'
#去掉所有空格
num_org=re.sub('\s+','',num_org)

while 1:
    try:
        num_withbrcket=brcket(num_org)

        num_without_brcket=num_withbrcket.replace('(','')
        num_without_brcket=num_without_brcket.replace(')','')
        while 1:
            try:
                num_without_brcket=multi_div(num_without_brcket)
            except Exception:
                break
        while 1:
            try:
                num_without_brcket=add_min(num_without_brcket)
            except Exception:
                break
        # print(num_without_brcket)
        num_org=num_org.replace(num_withbrcket,num_without_brcket)
        # print(num_withbrcket)
    except Exception:
        break

#已经去掉了所有括号，最后循环一遍乘除和加减
while 1:
    try:
        num_org=multi_div(num_org)
    except Exception:
        break
    while 1:
        try:
            num_org=add_min(num_org)
        except Exception:
            break
print(num_org)