python3 re模块，正则表达式方式实现简单加减乘除计算器
import re
#加法
def plus(s):
if re.search("^\d+[.]?\d*\+\d+[.]?\d*",s) != None:
str_re = re.search("\d+[.]?\d*\+\d+[.]?\d*", s).group()
x = float(re.search("^\d+[.]?\d*",str_re).group())
y = float(re.search("\d+[.]?\d*$",str_re).group())
result = str('{:.15f}'.format(x+y))
return result
elif re.search("^\-\d+[.]?\d*\+",s) != None:
str_re = re.search("^\-\d+[.]?\d*\+\d+[.]?\d*", s).group()
x = float(re.search("^\-\d+[.]?\d*", str_re).group())
y = float(re.search("\d+[.]?\d*$", str_re).group())
result = str('{:.15f}'.format(x+y))
return result
#减法
def minus(s):
if re.search("^\d+[.]?\d*\-\d+[.]?\d*",s) != None:
str_re = re.search("\d+[.]?\d*\-\d+[.]?\d*", s).group()
x = float(re.search("^\d+[.]?\d*",str_re).group())
y = float(re.search("\d+[.]?\d*$",str_re).group())
result = str('{:.15f}'.format(x-y))
return result
elif re.search("^\-\d+[.]?\d*\-",s) != None:
str_re = re.search("^\-\d+[.]?\d*\-\d+[.]?\d*", s).group()
x = float(re.search("^\-\d+[.]?\d*", str_re).group())
y = float(re.search("\d+[.]?\d*$", str_re).group())
result = str('{:.15f}'.format(x-y))
return result
elif re.search('^\-\d+[.]?\d*$',s) != None:
str_re = re.search('^\-\d+[.]?\d*$',s).group()
return str_re
#乘法
def mutiply(s):
if re.search("^[\-]?\d+[.]?\d*\*[\-]?\d+[.]?\d*",s) != None:
str_re = re.search("[\-]?\d+[.]?\d*\*[\-]?\d+[.]?\d*", s).group()
x = float(re.search("^[\-]?\d+[.]?\d*",str_re).group())
y = float(re.search("[\-]?\d+[.]?\d*$",str_re).group())
result = str('{:.15f}'.format(x*y)) # 设定小数位数限制
return result
else:
err = 'Maybe anything is Error!'
return err
#除法
def division(s):
if re.search("^[\-]?\d+[.]?\d*\/[\-]?\d+[.]?\d*",s) != None:
str_re = re.search("[\-]?\d+[.]?\d*\/[\-]?\d+[.]?\d*", s).group()
x = float(re.search("^[\-]?\d+[.]?\d*",str_re).group())
y = float(re.search("[\-]?\d+[.]?\d*$",str_re).group())
result = str('{:.15f}'.format(x/y)) #设定小数位数限制
return result
else:
err = 'Maybe anything is Error!'
return err
#检查是否有中文，有中文返回True
def check_zh(s):
check_zh = ('\u4e00' <= i <= '\u9fa5' for i in s)
for zh in check_zh:
if zh:
return True
else:
continue
#检查输入的计算式是否有错误，此处做中间空格删除处理，有字母中文报错
def check_str(s):
checkblank_list = re.findall('\s',s)
checkword_list = re.findall('[A-Za-z]',s)
if check_zh(s):
err = "Error:计算式中出现中文！"
print(err)
return False
if re.findall('[+\-*/(]$',s):
print('计算式结尾不能为+ - * / ( ')
return False
if re.findall('[（）]',s): #中文括号替换为英文的
#print('Error:计算式中出现文括号！')
s = re.sub('（','(',s)
s = re.sub('）',')',s)
#return False
if checkblank_list and (not checkword_list):
s_list=re.split(' ',s)
#print (s_list)
s = ''.join(s_list)
s_list = list(s)
i = s_list.count('(')
k = s_list.count(')')
if i == k: #检查括号前括号和后括号数量是否匹配
return s
else:
print("The brackets Error,Pls Check!")
return False
elif (not checkword_list) and (not checkword_list):
s_list = list(s)
i = s_list.count('(')
k = s_list.count(')')
if i == k:#检查括号前括号和后括号数量是否匹配
return s
else:
print("The brackets Error,Pls Check!")
return False
else:
err = "ERR:\nThe inputting expression evaluation Error！Pls try again！"
print(err)
#计算结果后的+- 和--情况替换
def format_str(s):
while True:
if re.findall('(\+\-)|(\-\-)',s):
if re.findall('^\-\-',s):
s = re.sub('^\-\-','',s)
s = re.sub('\+\-','-',s)
s = re.sub('\-\-', '+', s)
continue
else:
break
return s
#括号内计算
def bracket_rules(s):
old_s = s
while re.findall("\([^()]+\)",old_s):
#print('计算式：',old_s)
inner_bracket = re.search("\([^()]+\)",old_s).group()
inner_bracket_str = re.search('[^()]+',inner_bracket).group()#去掉括号
if re.findall('^[\-]?\d+[.]?\d*$',inner_bracket_str):
old_s = old_s.replace(inner_bracket,inner_bracket_str)
old_s = format_str(old_s)
continue
result_bracket = no_bracket_rules(inner_bracket_str)
old_s = old_s.replace(inner_bracket,result_bracket)
return old_s
#无括号时四则混合运算
def no_bracket_rules(s):
result_str = s
while not re.findall('^[\-]?\d+[.]?\d*$',result_str):
#print("计算式：",result_str)
if re.findall('(\*)|(\/)',result_str):
f = re.search("(\*)|(\/)",result_str).group()
if f =="*":
# if re.findall('\d+[.]?\d*\*[\-]?\d+[.]?\d*',result_str):
exprssion = re.search('\d+[.]?\d*\*[\-]?\d+[.]?\d*',result_str).group()
result = mutiply(exprssion) #乘法结果
#print("%s 结果：%s" % (exprssion, result))
result_str = result_str.replace(exprssion,result)
result_str = format_str(result_str)
continue
elif f == '/':
# elif re.findall('\d+[.]?\d*\/[\-]?\d+[.]?\d*',result_str):
exprssion = re.search('\d+[.]?\d*\/[\-]?\d+[.]?\d*',result_str).group()
result = division(exprssion)
#print("%s 结果：%s" % (exprssion, result))
result_str = result_str.replace(exprssion, result)
result_str = format_str(result_str)
continue
elif re.findall('(\-)|(\+)',result_str):
f2 = re.search("(\-)|(\+)",result_str).group()
if f2 =='+':
# if re.findall("(\d+[.]?\d*\+\d+[.]?\d*)|(^\-\d+[.]?\d*\+)",result_str):
exprssion = re.search('(\d+[.]?\d*\+[\-]?\d+[.]?\d*)|(^[\-]?\d+[.]?\d*\+[\-]?\d+[.]?\d*)', result_str).group()
result = plus(exprssion)
#print("%s 结果：%s" % (exprssion, result))
result_str = result_str.replace(exprssion, result)
result_str = format_str(result_str)
continue
elif f2 == '-':
if re.search('(\d+[.]?\d*\-[\-]?\d+[.]?\d*)|(^[\-]?\d+[.]?\d*\-[\-]?\d+[.]?\d*)',result_str):
# elif re.findall("(\d+[.]?\d*\-\d+[.]?\d*)|(^\-\d+[.]?\d*\-\d+[.]?\d+)",result_str):
exprssion = re.search('(\d+[.]?\d*\-[\-]?\d+[.]?\d*)|(^[\-]?\d+[.]?\d*\-[\-]?\d+[.]?\d*)',result_str).group()
result = minus(exprssion)
#print("%s 结果：%s" % (exprssion, result))
result_str = result_str.replace(exprssion, result)
result_str = format_str(result_str)
continue
elif re.search('^[\-]?\d+[.]?\d*\+[\-]?\d+[.]?\d*',result_str):
exprssion = re.search('^[\-]?\d+[.]?\d*\+[\-]?\d+[.]?\d*',result_str).group()
result = plus(exprssion)
#print("%s 结果：%s"%(exprssion,result))
result_str = result_str.replace(exprssion, result)
result_str = format_str(result_str)
continue
return result_str
#计算
def calculator(expression):
if re.findall('[()]',expression):
result_bracket = bracket_rules(expression)
result = no_bracket_rules(result_bracket)
return result
elif re.findall('[^()]',expression):
result = no_bracket_rules(expression)
return result
#执行计算
def running_calculator():
while True:
expression = input("----------------\nPlease input + - * / ( ) to calculate\n[q exit]\033[1;36;43m>>:\033[0m ").strip()
check_s = check_str(expression)
if len(expression) == 0:continue
elif expression == 'q':
print("Exit Calculator...")
break
elif check_s:
result = calculator(check_s)
print("\033[1;36;43m❤The END Result:\033[0m", result)
else:
continue
#启动运行
running_calculator()位数多了·· 出错~~~ @_@ 计算过程中小数位数太多用e- 表示时会有问题···死循环 规避该问题 格式化小数位数
result = str('{:.15f}'.format(x*y)) # 设定小数位数限制result = str('{:.15f}'.format(x/y)) #设定小数位数限制