Python之字符串计算（计算器）

import re

expression = '-1-2*((60+2*(-3-40.0+42425/5)*(9-2*5/3+357/553/3*99/4*2998+10*568/14))-(-4*3)/(16-3*2))+56+(56-45)'

question = eval(expression)

print(question)

def arithmetic(expression='1+1'):

    #     content = re.search('\(([\-\+\*\/]*\d+\.?\d*)+\)', expression)  # (-3-40.0/5)

    content = re.search('\(([-+*/]*\d+\.?\d*)+\)', expression)  # (-3-40.0/5)

    print(111, content)

    if content:

        content = content.group()

        content = content[1:-1]

        print('content:', content)

        replace_content = next_arithmetic(content)

        expression = re.sub('\(([-+*/]*\d+\.?\d*)+\)', replace_content, expression, count=1)

        print('next_expression:', expression)

    else:

        answer = next_arithmetic(expression)

        return answer

    return arithmetic(expression)

def next_arithmetic(content):

    while True:

        next_content_mul_div = re.search('\d+\.?\d*[*/][-+]?\d+\.?\d*', content)  # 找出带有*/的式子

        if next_content_mul_div:  # 如果content含有带有*/的式子

            next_content_mul_div = next_content_mul_div.group()

            print('next_content_mul_div:', next_content_mul_div)

            mul_div_content = mul_div(next_content_mul_div)  # 计算出带有*/的式子

            print('mul_div_content:', mul_div_content)

            content = re.sub('\d+\.?\d*[*/][-+]?\d+\.?\d*', str(mul_div_content), content, count=1)  # 把带有*/的式子计算出来后替换掉

            print('content:', content)

            continue

        next_content_add_sub = re.search('-?\d+\.?\d*[-+][-+]?\d+\.?\d*', content)  # 找出带有-+的式子

        if next_content_add_sub:  # 如果content含有带有+-的式子

            next_content_add_sub = next_content_add_sub.group()

            print('next_content_add_sub:', next_content_add_sub)

            add_sub_content = add_sub(next_content_add_sub)  # 计算出带有-+的式子

            print('add_sub_content:', add_sub_content)

            add_sub_content = str(add_sub_content)

            content = re.sub('-?\d+\.?\d*[-+]-?\d+\.?\d*', str(add_sub_content), content, count=1)  # 把带有-+的式子计算出来后替换掉

            print('content:', content)

            continue

        else:

            break

    return content

def add_sub(content):

    if '+' in content:

        content = content.split('+')

        print(content)

        content = float(content[0]) + float(content[1])

        return content

    elif '-' in content:

        content = content.split('-')

        # 减法情况有多种

        if content[0] == '-' and content[2] == '-':

            # content = content.split('-')

            print(content)

            content = -float(content[1]) - float(content[-1])

            return content

        if content[0] == '-':

            # content = content.split('-')

            print(content)

            content = -float(content[1]) - float(content[-1])

            return content

        if content[1] == '-' and content[2] == '-':

            # content = content.split('-')

            print(content)

            content = -float(content[0]) + float(content[-1])

            return content

        if content[1] == '':

            # content = content.split('-')

            print(content)

            content = float(content[0]) - float(content[2])

            return content

        if content[0] == '' and content[2] != '':

            print(content)

            content = -float(content[1]) - float(content[2])

            return content

        if content[0] == '' and content[2] == '':

            print(content)

            content = -float(content[1]) + float(content[3])

            return content

        else:

            # content = content.split('-')

            print(content)

            content = float(content[0]) - float(content[1])

            return content

def mul_div(content):

    if '*' in content:

        content = content.split('*')

        print(content)

        content = float(content[0]) * float(content[1])

        return content

    elif '/' in content:

        content = content.split('/')

        print(content)

        content = float(content[0]) / float(content[1])

        return content

# expression = '1-2*((60+2*(-3-40.0/5)*(9-2*5/3+7/3*99/4*2998+10*568/14))-(-4*3)/(16-3*2))'

expression = '-1-2*((60+2*(-3-40.0+42425/5)*(9-2*5/3+357/553/3*99/4*2998+10*568/14))-(-4*3)/(16-3*2))+56+(56-45)'

answer = arithmetic(expression)

print(answer)