I made a program of calculator in PYTHON 3, but showing traceback error.

Question

I have made a Simple calculator programing by python 3. But It is showing traceback error. I couldn't find the mistake. Someone please help me out. Here is the code below -
while True :
print ('Simple Calculator')
print ('Options')
print ('Enter add for addition')
print ('Enter sub for subtract')
print ('Enyer mult for multifunction')
print ('Enter dev for division')
num_1 = float (input ('Enter a number'))
num_2 = float (input ('Enter another number'))
if user_input == 'add':
result = str(num_1 + num_2)
print ('Answer: ' + result )
elif user_input == 'sub':
result = str(num_1 - num_2)
print ('Answer: ' + result )
elif user_input == 'mult':
result = str (num_1 * num_2)
print('Answer: '+result)
elif user_input == 'dev':
result = str(num_1 / num_2 )
print ('Answer: '+result)
https://code.sololearn.com/cE8d7gvX0hCY/?ref=app

Answer 1

as addition to William M
Instead of while True:
while user_input != "quit":

That helps a bit but u still have to enter
add
2
3
sub
5
4
quit

Answer 2

Just define user_input, you wrote "if user_input" but you did not define user_input. Just write before num_1, user_input = input().

But... you will still get an error. Why?
Because in solo learn you can just give an input one time. If you want to repare it remove while. While-loop would just work on your pc.

Answer 3

I did some touch-ups

https://code.sololearn.com/c321a5MNmJ2f/?ref=app