开发一个简单的python计算器
- 实现加减乘除及拓号优先级解析
- 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(不能调用eval等类似功能偷懒实现)，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
hint:
re.search(r'\([^()]+\)',s).group()
'(-40/5)'
- 输入用re搜索返回NONE的情况，也就是输入了全部是英文字母的情况；
- 输入的括号，左括号和右括号的个数不匹配的情况，肯定少输入；
- 输入含有非数字以及加减乘除或者括号的情况；搜索返回的字符的个数小于用户输入的长度；
# !/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:lzd import re def main():
while True:
a=input("请输入你想计算的数学方程式，先小括号（请输入半角的括号，不要输入中文的），后加减乘除\n")
#a=' 1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )'
a = a.replace(' ', '')
# print(a)
if re.search(r"[0-9\+\-\*/()\.]+", a) == None:
print("匹配失败，输入格式错误，请重新输入\n")
continue
elif a.count('(') != a.count(')'):
print('你写的括号左右个数不匹配')
continue
elif len(re.search(r"[0-9\+\-\*/()\.]+", a).group()) != len(a):
print("输入格式错误，请重新输入\n")
continue
else:
while True:
if '(' in a:
ct = re.search(r'\([^()]+\)', a) #计算出第一个()里的算式
if ct is not None:
b = ct.group()
c = chengfa_chufa(b)
a = re.sub(r'\(([^()]+)\)', str(c), a, 1) print(a)
else:
c = chengfa_chufa(a)
print(c)
break
break def jiajianfa(a):
'''
计算加减法
:param:
:return:
''' if '--' in a:
a = a.replace('--', '+') c = re.findall(r'-?\d+\.?\d*', a) #-123456.132123
ls = []
for i in c:
ls.append(float(i))
rest = sum(ls)
return rest def chengfa(a):
'''
计算乘法
:param ct:
:return:
''' b = re.search(r'\d+\.?\d*(\*-?\d+\.?\d*)+', a) #132132.654645*-564564.456456*-5645645.654561651615
if b is not None:
b = b.group()
rest = 1
c = re.findall(r'-?\d+\.?\d*', b)
ls = []
for item in c:
ls.append(float(item))
for i1 in range(len(ls)):
rest = rest * ls[i1]
a = re.sub(r'\d+\.?\d*(\*-?\d+\.?\d*)+', str(rest), a, 1)
return a def chufa(a):
'''
计算出发
:param a:
:return:
''' b = re.search(r'\d+\.?\d*(\/-?\d+\.?\d*)+', a) #523.5564561/-1231.564564/-1344.4546
if b is not None:
b = b.group()
c = re.findall(r'-?\d+\.?\d*', b)
ls = []
for i in c:
ls.append(float(i))
rest = ls[0]
for i1 in range(1, len(ls)):
rest = rest / ls[i1]
a = re.sub(r'\d+\.?\d*(\/-?\d+\.?\d*)+', str(rest), a, 1)
return a def chengfa_chufa(b):
'''
计算结果
:return:
'''
while True:
if '*' in b:
c = b.split('*')
if '/' in c[0]:
b = chufa(b)
else:
b = chengfa(b)
elif '/' in b:
b = chufa(b) elif '+' or '-' in b:
b = jiajianfa(b)
return b
else:
return b main()