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import re

class OPERATION(object):

def __init__(self, a, b,ys):

self.a = a

self.b = b

self.ys=ys

def addition(self):

result = self.a + self.b

print(' = %s' % result)

return result

def subtraction(self):

result = self.a - self.b

print(' = %s' % result)

return result

def  multiplication (self):

result = self.a * self.b

print(' = %s' % result)

return result

def division(self):

if self.b==0:

return print("输入有误")

else:

result = self.a / self.b

print(' = %s' % result)

return result

def operation(self):

if self.ys is '+':

OPERATION.addition(self)

elif self.ys is '-':

OPERATION.subtraction(self)

elif self.ys is '*':

OPERATION. multiplication (self)

elif self.ys is '/':

OPERATION.division(self)

else:

print("暂时没有实现62616964757a686964616fe78988e69d8331333433633362这种运算")

def main():

print("请输要计算的算式，如 a+b 按回车键查看结果,输入exit退出")

while True:

str = input(">>")

if str =='exit':

break;

else:

ret = re.match(r'^(\d+)([\+\-\*/]+)(\d+)', str)

if ret:

numa = int(ret.group(1))

operationalCharacter = ret.group(2)

numb = int(ret.group(3))

print(numa, operationalCharacter, numb,end='')

yunsuan = OPERATION(numa, numb,operationalCharacter)

yunsuan.operation()

else:

print("请检查输入是否正确")

if __name__=='__main__':

main()

运行结果