"""
封装一个计算器函数
计算器功能：仅支持加减乘除运算
转载https://blog.csdn.net/a971956955/article/details/81489914
"""

import re


def eq_format(eq):
    '''
    :param eq: 输入的算式字符串
    :return: 格式化以后的列表，如['60','+','7','*','8']
    '''
    format_list = re.findall('[\d\.]+|\(|\+|\-|\*|\/|\)', eq)
    return format_list


def change(eq, count):
    '''
    :param eq: 刚去完括号或者乘除后的格式化列表
    :param count: 发生变化的元素的索引
    :return: 返回一个不存在 '+-' ,'--'类的格式化列表
    '''
    if eq[count] == '-':
        if eq[count - 1] == '-':
            eq[count - 1] = '+'
            del eq[count]
        elif eq[count - 1] == '+':
            eq[count - 1] = '-'
            del eq[count]
    return eq


def remove_multiplication_division(eq):
    '''
    :param eq: 带有乘除号的格式化列表
    :return: 去除了乘除号的格式化列表
    '''
    count = 0
    for i in eq:
        if i == '*':
            if eq[count + 1] != '-':
                eq[count - 1] = float(eq[count - 1]) * float(eq[count + 1])
                del (eq[count])
                del (eq[count])
            elif eq[count + 1] == '-':
                eq[count] = float(eq[count - 1]) * float(eq[count + 2])
                eq[count - 1] = '-'
                del (eq[count + 1])
                del (eq[count + 1])
            eq = change(eq, count - 1)
            return remove_multiplication_division(eq)
        elif i == '/':
            if eq[count + 1] != '-':
                eq[count - 1] = float(eq[count - 1]) / float(eq[count + 1])
                del (eq[count])
                del (eq[count])
            elif eq[count + 1] == '-':
                eq[count] = float(eq[count - 1]) / float(eq[count + 2])
                eq[count - 1] = '-'
                del (eq[count + 1])
                del (eq[count + 1])
            eq = change(eq, count - 1)
            return remove_multiplication_division(eq)
        count = count + 1
    return eq


def remove_plus_minus(eq):
    '''
    :param eq: 只带有加减号的格式化列表
    :return: 计算出整个列表的结果
    '''
    count = 0
    if eq[0] != '-':
        sum = float(eq[0])
    else:
        sum = 0.0
    for i in eq:
        if i == '-':
            sum = sum - float(eq[count + 1])
        elif i == '+':
            sum = sum + float(eq[count + 1])
        count = count + 1
    if sum >= 0:
        eq = [str(sum)]
    else:
        eq = ['-', str(-sum)]
    return eq


def calculate(s_eq):
    '''
    :param s_eq: 不带括号的格式化列表
    :return: 计算结果
    '''
    if '*' or '/' in s_eq:
        s_eq = remove_multiplication_division(s_eq)
    if '+' or '-' in s_eq:
        s_eq = remove_plus_minus(s_eq)
    return s_eq


def simplify(format_list):
    '''
    :param format_list: 输入的算式格式化列表如['60','+','7','*','8']
    :return: 通过递归去括号，返回简化后的列表
    '''

    bracket = 0  # 用于存放左括号在格式化列表中的索引
    count = 0
    for i in format_list:
        if i == '(':
            bracket = count
        elif i == ')':
            temp = format_list[bracket + 1: count]
            # print(temp)
            new_temp = calculate(temp)
            format_list = format_list[:bracket] + new_temp + format_list[count + 1:]
            format_list = change(format_list, bracket)  # 解决去括号后会出现的--  +- 问题
            return simplify(format_list)  # 递归去括号
        count = count + 1
    return format_list  # 当递归到最后一层的时候，不再有括号，因此返回列表


def caculator(eq):
    format_list = eq_format(eq)
    s_eq = simplify(format_list)
    ans = calculate(s_eq)
    if len(ans) == 2:
        ans = -float(ans[1])
    else:
        ans = float(ans[0])
    return ans

if __name__ == '__main__':
    equation = '1-2*((60-30+(-40/5)*(9-2*5/3+7/3*99/4*2998+10*568/14))-(-4*3)/(16-3*2))'
    ans = caculator(equation)
    print('eval运算结果：', eval(equation))
    print('程序运算结果：', ans)