#! /usr/bin/env python
import os,subprocess
from stat import *
#! /bin/bash 
clear 
_rc = subprocess.call(["clear"])
sum=0 
sum=0
i="y" 
i="y"
echo " Enter one no." 
print(" Enter one no.")
read n1 
n1 = raw_input()
echo "Enter second no." 
print("Enter second no.")
read n2 
n2 = raw_input()
while [ $i = "y" ] 
do 
echo "1.Addition" 
echo "2.Subtraction" 
echo "3.Multiplication" 
echo "4.Division" 
echo "Enter your choice" 
read ch 
case $ch in 
    1)sum=`expr $n1 + $n2` 
     echo "Sum = $sum";; 
    2)sum=`expr $n1 - $n2` 
     echo "Sub = $sum";; 
    3)sum=`expr $n1 \* $n2` 
     echo "Mul = $sum";; 
    4)sum=`expr $n1 / $n2` 
     echo "Div = $sum";; 
    *)echo "Invalid choice";; 
esac 
echo "Do u want to continue (y/n)) ?" 
read i 
if [ $i != "y" ] 
then 
    exit 
fi
done
while (i == ""y"" ):
    print("1.Addition")
    print("2.Subtraction")
    print("3.Multiplication")
    print("4.Division")
    print("Enter your choice")
    ch = raw_input()
    
    if ( ch == '1'):
        sum=os.popen("expr "+str(n1)++str(n2)).read()
        print("Sum = " + str(sum))
    elif ( ch == '2'):
        sum=os.popen("expr "+str(n1)+" - "+str(n2)).read()
        print("Sub = " + str(sum))
    elif ( ch == '3'):
        sum=os.popen("expr "+str(n1)+" * "+str(n2)).read()
        print("Mul = " + str(sum))
    elif ( ch == '4'):
        sum=os.popen("expr "+str(n1)+" / "+str(n2)).read()
        print("Div = " + str(sum))
    else:
        print("Invalid choice")
    print("Do u want to continue (y/n)) ?")
    i = raw_input()
    if (i != ""y""  ):
        exit()
ÿ