CODEWITHSUNDEEP
pythonclassooprecursion
Michael Brennan
Michael Brennan

Reputation: 848

Recursive call causing IndexError in Class function

The goal of my program is to have the computer ask a user questions, and return some specifications for a computer that would fit their needs. Right now I am working on QuestionAsker, which is responsible for, as the class name suggests, asking the user questions. I've been hung up on the 4th line of AskQuestion() function. Before I tell you the problem, take a look at the code:

from question import Question

class QuestionAsker():
    questions = [
        Question("At minimum, what should your game be running on?", ["Low", "Medium", "Ultra"]),
        Question("On a scale of 1-3, how much flair do you want on your computer?", ["Low", "Medium", "Ultra"]),
        Question("Money doesn't grow on trees. How much money is in your budget?", ["$500", "$1000", "$2000+"]),
        ]

    index = 0   
    def AskQuestion(self):
        userInputForQuestion = raw_input(self.questions[self.index].question + " ")

        if userInputForQuestion not in self.questions[self.index].answers:
            print("Try again.")
            self.AskQuestion()


        self.questions[self.index].selectedAnswer = userInputForQuestion

        self.index += 1;

    def resetIndex(self):
        self.index = 0

    def ReadQuestions(self):
        pass

I was testing this code by calling AskQuestion a couple of times (to loop through all the questions), and to make sure this code was tippy top, I supplied multiple answers that returned "Try again," as it should. The issue is that if I supplied more than 1 wrong answer to a question, but then if I answered correctly after multiple wrong answers, I would get the following error message:

IndexError: list index out of range

I immediately suspected the [self.index] of the self.questions[self.index], so I began printing out the index to the console. I thought that the issue was that the AskQuestion was magically incrementing the self.index, on the final line of the AskQuestion function, but no. It kept printing a consistent number, in the case of the first question, 0!

I'm at my wits end here, and the other questions I've seen on this haven't served much help. Hopefully you guys can help, thanks!

Upvotes: 0

Views: 38

Answers (1)

Rockybilly
Rockybilly

Reputation: 4510

Please take care that in your function body, when a wrong answer is given, the function does not end. It makes a recursive call. When that call ends, the index is still incremented. So the wrong answers still mess the index up.

You should end the function after the wrong call is made, for what you want to happen.

if userInputForQuestion not in self.questions[self.index].answers:
    print("Try again.")
    self.AskQuestion()
    return None

or use else.

if userInputForQuestion not in self.questions[self.index].answers:
    print("Try again.")
    self.AskQuestion()
else:
    self.questions[self.index].selectedAnswer = userInputForQuestion
    self.index += 1;

Also please note that using recursion in such a way is not very common. Which made you make the mistake anyway.

Upvotes: 1

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