How to fix my code's error "List index out of range"

Question

How do I fix the error my code comes up with the following?

Traceback (most recent call last):
   File "main.py", line 143, in <module>
     print(question_list2[random_int])
IndexError: list index out of range

This is the code in question:

question_list2 = []

question_list2.append(" the marines are ___ based opreatives  ")
question_list2.append(" for under water travel marines use _____ ")
question_list2.append(" the avergae marine trains for _ weeks ")

answer_list2 = []

answer_list2.append("sea")
answer_list2.append("subamrines")
answer_list2.append("13")

top_index = 4
correct = 0

for i in range (0,4):

    random_int = random.randint(0,top_index)

    print(question_list2[random_int])

    top_index = top_index - 1

    user_answer1 = input("fill in the blank with the correct word ")

    if user_answer == answer_list1[random_int]:

        correct = correct + 3

    del question_list1[random_int]
    del answer_list1[random_int]

Try printing out random_int on the line before the error. It would seem you can get a value that is not a valid index for question_list2. — Paul Rooney
– Paul Rooney, Commented Jun 11, 2019 at 23:35
You are setting random int from 0-4 which is inclusive, meaning 4 is a possible output. Your list is only 3 long to begin with which is a problem in and of itself. As you del elements from the list, the list gets shorter, at which point, answer_list1[3] will also throw an error. Try to search for a basic tutorial online about python list and indexing. — sin tribu
– sin tribu, Commented Jun 11, 2019 at 23:37

Mark · Accepted Answer · 2019-06-11 23:50:56Z

From the random docs

random.randint(a, b)
Return a random integer N such that a <= N <= b

This means that:

top_index = 4
random_int = random.randint(0,top_index)

Has the possibility of setting random_int to 3 or 4 which are outside the range of your list which only has three items with index 0, 1, and 2.

Rather than mutating your lists and using indexes, it might be easier to make a list of indexes, shuffle it, then iterate over it:

indexes = random.sample(range(0, len(question_list)), k = len(question_list))

for i in indexes:
    # etc...

If you kept the questions and answers together in a single list, you could do away with the indexes altogether. This would be a good use for named tuples

import random
from collections import namedtuple

qa = namedtuple('QA', ['question', 'answer'])

question_list = [
    qa(" the marines are ___ based opreatives  ", 'sea'),
    qa(" for under water travel marines use _____ ",'submarines'),
    qa(" the avergae marine trains for _ weeks ", '13')
]

random.shuffle(question_list)

correct = 0
for qa in question_list:
    print(qa.question)
    user_answer = input("fill in the blank with the correct word ")

    if user_answer == qa.answer:
        correct = correct + 1

Peter Mortensen · Accepted Answer · 2019-06-14 11:26:13Z

0

I believe that you only have three things on your list. The range should be range(0,3) and maybe your top_index should be top_index = 2.

Since the indexes on your list are [0,1,2]

The first item in list > index = 0

The second item in list > index = 1

The third item in list > index = 2

edited Jun 14, 2019 at 11:26

Peter Mortensen

31.4k22 gold badges110 silver badges134 bronze badges

answered Jun 11, 2019 at 23:38

Leandro A.G.

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