localize-fault-code.md

A task

Visit Python Tutor and open a blank Python 2.7 editor. Paste in the code below and try to compute 1+1, noticing that the output is "Invalid input" instead of 2. Find out why and propose a change to the program to fix the bug.

''' Program make a simple calculator that can add, subtract, multiply and divide using functions '''

# This function adds two numbers
def add(x, y):
   return x + y

# This function subtracts two numbers
def subtract(x, y):
   return x - y

# This function multiplies two numbers
def multiply(x, y):
   return x * y

# This function divides two numbers
def divide(x, y):
   return x / y

print("Select operation.")
print("1.Add")
print("2.Subtract")
print("3.Multiply")
print("4.Divide")

# Take input from the user
choice = input("Choose operation:")

num1 = int(input("Enter first number: "))
num2 = int(input("Enter second number: "))

if choice == '1':
   print(num1,"+",num2,"=", add(num1,num2))

elif choice == '2':
   print(num1,"-",num2,"=", subtract(num1,num2))

elif choice == '3':
   print(num1,"*",num2,"=", multiply(num1,num2))

elif choice == '4':
   print(num1,"/",num2,"=", divide(num1,num2))
else:
   print("Invalid input")