类函数中递归调用引发IndexError问题排查

Let's break down why you're hitting that IndexError and fix it right away.

The Root Cause #

Your issue comes from using recursion to handle invalid input. Here's what's happening step-by-step when you enter multiple wrong answers then a correct one:

1. You call AskQuestion() with index = 0
2. Input is invalid → you recursively call AskQuestion() again (still index = 0)
3. Input is valid this time → the recursive call sets the selected answer, increments index to 1, and returns to the original call
4. The original call resumes execution, increments index again to 2
5. If you call AskQuestion() again, it increments to 3, which is beyond your questions list's bounds (indices 0-2) → boom, IndexError

Every recursive layer runs the self.index +=1 line, leading to over-incrementing.

The Fix: Use a Loop Instead of Recursion #

Recursion is overkill here—loops are far more reliable for repeated input validation. Replace your AskQuestion() method with this:

def AskQuestion(self):
    # Loop until we get a valid answer
    while True:
        userInputForQuestion = raw_input(self.questions[self.index].question + " ")
        if userInputForQuestion in self.questions[self.index].answers:
            self.questions[self.index].selectedAnswer = userInputForQuestion
            self.index += 1
            break  # Exit loop once valid input is received
        print("Try again.")

Why This Works #

• The loop keeps asking for input until the user enters a valid option
• self.index +=1 only runs once per valid answer, so you'll never accidentally jump past the end of your questions list
• It avoids the stack overflow risk that comes with deep recursion (unlikely here, but still a good practice)

If You Insist on Using Recursion (Not Recommended) #

If you want to keep the recursive pattern for some reason, add a return statement right after the recursive call to prevent the original layer from incrementing the index again:

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()
        return  # Stop execution here so we don't increment index twice
    self.questions[self.index].selectedAnswer = userInputForQuestion
    self.index += 1

But again, the loop approach is cleaner and more maintainable for this use case.

内容的提问来源于stack exchange，提问作者Michael Brennan