Does moving guesses.append(guess) to the end of the else clause really make a difference?

Question

At 4:20 Kenneth is suggesting that guesses.append(guess) should be moved to the end of the else clause in order to prevent breaking out of the loop before printing the messages, causing the user to not get any confirmation even if they get the answer on their 5th try. But this is a fundamental misunderstanding of the control flow of the while loop:
python
while len(guesses) < 5:
    try:
        # get a number guess from the player
        guess = int(input("Guess a number between 1 and 10: "))
    except ValueError:
        print("{} isn't a number!".format(guess))
    else:
        # compare guess to secret number
        if guess == secret_num:
            print("You got it! My number was {}".format(secret_num))
            break
        elif guess < secret_num:
            print("My number is higher than {}".format(guess))
        else:
            print("My number is lower than {}".format(guess))
        guesses.append(guess)

should be equivalent to:
python
while len(guesses) < 5:
    try:
        # get a number guess from the player
        guess = int(input("Guess a number between 1 and 10: "))
    except ValueError:
        print("{} isn't a number!".format(guess))
    else:
        guesses.append(guess)
        # compare guess to secret number
        if guess == secret_num:
            print("You got it! My number was {}".format(secret_num))
            break
        elif guess < secret_num:
            print("My number is higher than {}".format(guess))
        else:
            print("My number is lower than {}".format(guess))

The condition is only evaluated at the beginning of a new iteration of the while loop. Changing the length of the guesses list by appending to it and thereby possibly changing the boolean value of the "len(guesses) less than 5" expression should have absolutely no effect on the execution of the current iteration of the while loop - we won't break out of the while automagically at the moment when "len(guesses) == 5" if it happens somewhere in the middle of the current iteration.

Chris Freeman · Accepted Answer

You are correct that the guess append statement in either location has the same outcome for this program. 
If the program had intentions to do more with the previous guesses, then the earlier location would be preferred so that the last guess get appended before the while loop breaks. 
Tagging @Kenneth Love (https://teamtreehouse.com/kennethlove) for further comment.

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Boštjan Borič

Boštjan Borič

Does moving guesses.append(guess) to the end of the else clause really make a difference?

Boštjan Borič

Boštjan Borič

1 Answer

Chris Freeman

Chris Freeman