I ran it in python 3.6 and it worked fine. with the python 2.7 IDE it displayed "add" not defined

while True:

print("Options")

print("Enter 'add' to add two numbers")

print("Enter 'subtract' to subtract two numbers")

print("Enter 'multiply' to multiply two numbers")

print("Enter 'divide' to divide two numbers")

print("Enter 'quit' to quit the program ")

user_input =input(":")

if user_input == "quit":

   break     

elif user_input == "add":

  num1 = float(input("Enter a number \n"))        

  num2 = float(input("Enter another number \n"))  

  result =str(num1 + num2)      

     print("The answer is " + result)    

elif user_input == "subtract":

   num1 = float(input("Enter a number \n"))      

   num2 = float(input("Enter another number \n"))   

  result =str(num1 - num2)         

  print("The answer is " + result)  

elif user_input == "multiply":

   num1 = float(input("Enter a number \n"))    

   num2 = float(input("Enter another number \n"))    

   result =str(num1 \* num2)       

   print("The answer is " + result)   

elif user_input == "divide":

   num1 = float(input("Enter a number \n"))  

   num2 = float(input("Enter another number \n"))  

   result =str(num1 / num2)    

   print("The answer is " + result)   

else:

  print("Unknown Error")