Try Block Error

Hi there! This is a very common one for people to get tripped up on so you're not alone. But let's think for a minute about some basic rules about Python and what's happening here. First, in order to use a variable you must first assign it a value. In your case, you are declaring and initializing the variable selected_by_user in the try block. Then you take that and turn it into an integer (hopefully), but here's where the problem comes in. If the user enters something like "hello", then the conversion to an integer will fail. When this fails, the assignment to selected_by_user also fails. At this point, it jumps to the ValueError without selected_by_user being defined.

In your except clause you then try and print out an error to the user saying that you need a number and show the user what they put in. But you're trying to format the string with a value from a variable that isn't defined. Remember, that assignment failed.

The most elegant way to fix this (in my opinion) is to move the prompt to the user out of the try block. Then, inside the try block just do the conversion to integer.

Take a look:

def game():

    #get the input from the user no matter what it is
    selected_by_user = input("Please select a number between 1 and 10.")

    try:
        #try storing the result of the input converted to an integer
        selected_by_user = int(selected_by_user)
    except ValueError:
        print("Sorry, but {} is an invalid number".format(selected_by_user))
    else:
        print(selected_by_user)
game()

This will guarantee that your selected_by_user variable is defined and has a value to use to format that string even if the conversion to an integer fails.

Hope this helps!