python array list assignment index out of range

IndexError: list assignment index out of range in Python

Last updated: Apr 8, 2024 Reading time · 9 min

# Table of Contents

• IndexError: list assignment index out of range
• (CSV) IndexError: list index out of range
• sys.argv[1] IndexError: list index out of range
• IndexError: pop index out of range

Make sure to click on the correct subheading depending on your error message.

# IndexError: list assignment index out of range in Python

The Python "IndexError: list assignment index out of range" occurs when we try to assign a value at an index that doesn't exist in the list.

To solve the error, use the append() method to add an item to the end of the list, e.g. my_list.append('b') .

Here is an example of how the error occurs.

The list has a length of 3 . Since indexes in Python are zero-based, the first index in the list is 0 , and the last is 2 .

Trying to assign a value to any positive index outside the range of 0-2 would cause the IndexError .

# Adding an item to the end of the list with append()

If you need to add an item to the end of a list, use the list.append() method instead.

The list.append() method adds an item to the end of the list.

The method returns None as it mutates the original list.

# Changing the value of the element at the last index in the list

If you meant to change the value of the last index in the list, use -1 .

When the index starts with a minus, we start counting backward from the end of the list.

# Declaring a list that contains N elements and updating a certain index

Alternatively, you can declare a list that contains N elements with None values.

The item you specify in the list will be contained N times in the new list the operation returns.

Make sure to wrap the value you want to repeat in a list.

If the list contains a value at the specific index, then you are able to change it.

# Using a try/except statement to handle the error

If you need to handle the error if the specified list index doesn't exist, use a try/except statement.

The list in the example has 3 elements, so its last element has an index of 2 .

We wrapped the assignment in a try/except block, so the IndexError is handled by the except block.

You can also use a pass statement in the except block if you need to ignore the error.

The pass statement does nothing and is used when a statement is required syntactically but the program requires no action.

# Getting the length of a list

If you need to get the length of the list, use the len() function.

The len() function returns the length (the number of items) of an object.

The argument the function takes may be a sequence (a string, tuple, list, range or bytes) or a collection (a dictionary, set, or frozen set).

If you need to check if an index exists before assigning a value, use an if statement.

This means that you can check if the list's length is greater than the index you are trying to assign to.

# Trying to assign a value to an empty list at a specific index

Note that if you try to assign to an empty list at a specific index, you'd always get an IndexError .

You should print the list you are trying to access and its length to make sure the variable stores what you expect.

# Use the extend() method to add multiple items to the end of a list

If you need to add multiple items to the end of a list, use the extend() method.

The list.extend method takes an iterable (such as a list) and extends the list by appending all of the items from the iterable.

The list.extend method returns None as it mutates the original list.

# (CSV) IndexError: list index out of range in Python

The Python CSV "IndexError: list index out of range" occurs when we try to access a list at an index out of range, e.g. an empty row in a CSV file.

To solve the error, check if the row isn't empty before accessing it at an index, or check if the index exists in the list.

Assume we have the following CSV file.

And we are trying to read it as follows.

# Check if the list contains elements before accessing it

One way to solve the error is to check if the list contains any elements before accessing it at an index.

The if statement checks if the list is truthy on each iteration.

All values that are not truthy are considered falsy. The falsy values in Python are:

• constants defined to be falsy: None and False .
• 0 (zero) of any numeric type
• empty sequences and collections: "" (empty string), () (empty tuple), [] (empty list), {} (empty dictionary), set() (empty set), range(0) (empty range).

# Check if the index you are trying to access exists in the list

Alternatively, you can check whether the specific index you are trying to access exists in the list.

This means that you can check if the list's length is greater than the index you are trying to access.

# Use a try/except statement to handle the error

Alternatively, you can use a try/except block to handle the error.

We try to access the list of the current iteration at index 1 , and if an IndexError is raised, we can handle it in the except block or continue to the next iteration.

# sys.argv [1] IndexError: list index out of range in Python

The sys.argv "IndexError: list index out of range in Python" occurs when we run a Python script without specifying values for the required command line arguments.

To solve the error, provide values for the required arguments, e.g. python main.py first second .

I ran the script with python main.py .

The sys.argv list contains the command line arguments that were passed to the Python script.

# Provide all of the required command line arguments

To solve the error, make sure to provide all of the required command line arguments when running the script, e.g. python main.py first second .

Notice that the first item in the list is always the name of the script.

It is operating system dependent if this is the full pathname or not.

# Check if the sys.argv list contains the index

If you don't have to always specify all of the command line arguments that your script tries to access, use an if statement to check if the sys.argv list contains the index that you are trying to access.

I ran the script as python main.py without providing any command line arguments, so the condition wasn't met and the else block ran.

We tried accessing the list item at index 1 which raised an IndexError exception.

You can handle the error or use the pass keyword in the except block.

# IndexError: pop index out of range in Python

The Python "IndexError: pop index out of range" occurs when we pass an index that doesn't exist in the list to the pop() method.

To solve the error, pass an index that exists to the method or call the pop() method without arguments to remove the last item from the list.

The list has a length of 3 . Since indexes in Python are zero-based, the first item in the list has an index of 0 , and the last an index of 2 .

If you need to remove the last item in the list, call the method without passing it an index.

The list.pop method removes the item at the given position in the list and returns it.

You can also use negative indices to count backward, e.g. my_list.pop(-1) removes the last item of the list, and my_list.pop(-2) removes the second-to-last item.

Alternatively, you can check if an item at the specified index exists before passing it to pop() .

This means that you can check if the list's length is greater than the index you are passing to pop() .

An alternative approach to handle the error is to use a try/except block.

If calling the pop() method with the provided index raises an IndexError , the except block is run, where we can handle the error or use the pass keyword to ignore it.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• IndexError: index 0 is out of bounds for axis 0 with size 0
• IndexError: invalid index to scalar variable in Python
• IndexError: pop from empty list in Python [Solved]
• Replacement index 1 out of range for positional args tuple
• IndexError: too many indices for array in Python [Solved]
• IndexError: tuple index out of range in Python [Solved]

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Python List Index Out of Range – How to Fix IndexError

In Python, the IndexError is a common exception that occurs when trying to access an element in a list, tuple, or any other sequence using an index that is outside the valid range of indices for that sequence. List Index Out of Range Occur in Python when an item from a list is tried to be accessed that is outside the range of the list. Before we proceed to fix the error, let’s discuss how indexing work in Python .

What Causes an IndexError in Python

• Accessing Non-Existent Index: When you attempt to access an index of a sequence (such as a list or a string) that is out of range, an Indexerror is raised. Sequences in Python are zero-indexed, which means that the first element’s index is 0, the second element’s index is 1, and so on.
• Empty List: If you try to access an element from an empty list, an Indexerror will be raised since there are no elements in the list to access.

Example: Here our list is 3 and we are printing with size 4 so in this case, it will create a list index out of range.

Similarly, we can also get an Indexerror when using negative indices.

How to Fix IndexError in Python

• Check List Length: It’s important to check if an index is within the valid range of a list before accessing an element. To do so, you can use the function to determine the length of the list and make sure the index falls within the range of 0 to length-1.
• Use Conditional Statements: To handle potential errors, conditional statements like “if” or “else” blocks can be used. For example, an “if” statement can be used to verify if the index is valid before accessing the element. if or try-except blocks to handle the potential IndexError . For instance, you can use a if statement to check if the index is valid before accessing the element.

How to Fix List Index Out of Range in Python

Let’s see some examples that showed how we may solve the error.

• Using Python range()
• Using Python Index()
• Using Try Except Block

Python Fix List Index Out of Range using Range()

The range is used to give a specific range, and the Python range() function returns the sequence of the given number between the given range.

Python Fix List Index Out of Range u sing Index()

Here we are going to create a list and then try to iterate the list using the constant values in for loops.

Reason for the error –  The length of the list is 5 and if we are an iterating list on 6 then it will generate the error.

Solving this error without using Python len() or constant Value: To solve this error we will take the index of the last value of the list and then add one then it will become the exact value of length.

Python Fix List Index Out of Range using Try Except Block

If we expect that an index might be out of range, we can use a try-except block to handle the error gracefully.

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How to Fix IndexError: List Index Out of Range in Python

Table of Contents

The IndexError: list index out of range error occurs in Python when an item from a list is attempted to be accessed that is outside the index range of the list. The range of a list in Python is [0, n-1], where n is the number of elements in the list.

Python IndexError Example

Here’s an example of a Python IndexError: list index out of range thrown when trying to access an out of range list item:

In the above example, since the list test_list contains 4 elements, its last index is 3. Trying to access an element an index 4 throws an IndexError: list index out of range :

How to Fix IndexError in Python

The Python IndexError: list index out of range can be fixed by making sure any elements accessed in a list are within the index range of the list. This can be done by using the range() function along with the len() function.

The range() function returns a sequence of numbers starting from 0 ending at the integer passed as a parameter. The len() function returns the length of the parameter passed. Using these two methods together allows for safe iteration over the list up to its final element, thus ensuring that you stay within the valid index range and preventing the IndexError.

Here's how to use this approach to fix the error in the earlier example:

The above code runs successfully and produces the correct output as expected:

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Python indexerror: list index out of range Solution

IndexErrors are one of the most common types of runtime errors in Python. They’re raised when you try to access an index value inside a Python list that does not exist. In most cases, index errors are easy to resolve. You just need to do a little bit of debugging.

In this tutorial, we’re going to talk about the “indexerror: list index out of range” error. We’ll discuss how it works and walk through an example scenario where this error is present so that we can solve it.

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The problem: indexerror: list index out of range.

As always, the best place to start is to read and break down our error message: 

This error message tells us that we’re trying to access a value inside an array that does not have an index position.

In Python, index numbers start from 0 . Here’s a typical Python array:

This array contains three values. The first list element, Java, has the index value 0. Each subsequent value has an index number 1 greater than the last. For instance, Python’s index value is 1.

If we try to access an item at the index position 3, an error will be returned. The last item in our array has the index value 2.

Example Scenarios (and Solutions)

There are two common scenarios in which the “list index out of range” error is raised:

• When you try to iterate through a list and forget that lists are indexed from zero.
• When you forget to use range() to iterate over a list.

Let’s walk through both of these scenarios.

Lists Are Indexed From Zero

The following program prints out all the values in a list called “programming_languages” to the Python shell:

First, we have declared two variables. The variable “programming_languages” stores the list of languages that we want to print to the console. The variable “count” is used to track how many values we have printed out to the console.

Next, we have declared a while loop . This loop prints out the value from the “programming_languages” at the index position stored in “count”. Then, it adds 1 to the “count” variable. This loop continues until the value of “count” is no longer less than or equal to the length of the “programming_languages” list.

Let’s try to run our code:

All the values in our list are printed to the console but an error is raised. The problem is that our loop keeps going until the value of “count” is no longer less than or equal to the length of “programming_languages”. This means that its last iteration will check for:

This value does not exist. This causes an IndexError. To solve this problem, we can change our operator from <= to <. This will ensure that our list only iterates until the value of “count” is no longer less than the length of “programming_languages”. Let’s make this revision:

Our code returns:

We’ve successfully solved the error! Our loop is no longer trying to print out programming_languages[3]. It stops when the value of “count” is equal to 3 because 3 is not less than the length of “programming_languages”.

Forget to Use range()

When you’re iterating over a list of numbers, it’s easy to forget to include a range() statement . If you are accessing items in this list, an error may be raised.

Consider the following code:

This code should print out all the values inside the “ages” array. This array contains the ages of students in a middle school class. Let’s run our program and see what happens:

An error is raised. Let’s add a print statement inside our loop to see the value of “age” in each iteration to see what has happened:

The first age, 9, is printed to the console. However, the value of “age” is an actual value from “ages”. It’s not an index number. On the “print(ages[age])” line of code, we’re trying to access an age by its index number.

When we run our code, it checks for: ages[9]. The value of “age” is 9 in the first iteration. There is no item in our “ages” list with this value.

To solve this problem, we can use a range() statement to iterate through our list of ages:

Let’s run our code again:

All of the values from the “ages” array are printed to the console. The range() statement creates a list of numbers in a particular range. In this case, the range [0, 1, 2] is created. These numbers can then be used to access values in “ages” by their index number.

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Alternatively, we could use a “for…in” loop without using indexing:

This code returns:

Our code does not try to access any values by index from the “ages” array. Instead, our loop iterates through each value in the “ages” array and prints it to the console.

IndexErrors happen all the time. To solve the “indexerror: list index out of range” error, you should make sure that you’re not trying to access a non-existent item in a list.

If you are using a loop to access an item, make sure that loop accounts for the fact that lists are indexed from zero. If that does not solve the problem, check to make sure that you are using range() to access each item by its index value.

Now you’re ready to solve the “indexerror: list index out of range” error like a Python expert!

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How to fix an IndexError in Python

Yuko Honda on Flickr. CC BY-SA 2.0

If you use Python, you may have encountered the IndexError error in response to some code you've written. The IndexError message in Python is a runtime error. To understand what it is and how to fix it, you must first understand what an index is. A Python list (or array or dictionary ) has an index. The index of an item is its position within a list. To access an item in a list, you use its index. For instance, consider this Python list of fruits:

This list's range is 5, because an index in Python starts at 0.

• watermelon: 5

Suppose you need to print the fruit name pear from this list. You can use a simple print statement, along with the list name and the index of the item you want to print:

What causes an IndexError in Python?

What if you use an index number outside the range of the list? For example, try to print the index number 6 (which doesn't exist):

As expected, you get IndexError: list index out of range in response.

How to fix IndexError in Python

The only solution to fix the IndexError: list index out of range error is to ensure that the item you access from a list is within the range of the list. You can accomplish this by using the range() an len() functions.

The range() function outputs sequential numbers, starting with 0 by default, and stopping at the number before the specified value:

The len() function, in the context of a list, returns the number of items in the list:

List index out of range

By using range() and len() together, you can prevent index errors. The len() function returns the length of the list (6, in this example.) Using that length with range() becomes range(6) , which returns items at index 0, 1, 2, 3, 4, and 5.

Fix IndexError in Python loops

If you're not careful, index errors can happen in Python loops. Consider this loop:

The logic seems reasonable. You've defined n as a counter variable, and you've set the loop to occur until it equals the length of the list. The length of the list is 6, but its range is 5 (because Python starts its index at 0). The condition of the loop is n <= 6 , and so the while loop stops when the value of n is equal to 6:

• When n is 0 => apple
• When n is 1 => banana
• When n is 2 => orange
• When n is 3 => pear
• When n is 4 => grapes
• When n is 5 => watermelon
• When n is 6 => IndexError: list index out of range

When n is equal to 6, Python produces an IndexError: list index out of range error.

To avoid this error within Python loops, use only the < ("less than") operator, stopping the while loop at the last index of the list. This is one number short of the list's length:

There's another way to fix, this too, but I leave that to you to discover.

No more Python index errors

The ultimate cause of IndexError is an attempt to access an item that doesn't exist within a data structure. Using the range() and len() functions is one solution, and of course keep in mind that Python starts counting at 0, not 1.

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The Problem: indexerror: list assignment index out of range

When you receive an error message, the first thing you should do is read it. Because, an error message can tell you a lot about the nature of an error.

indexer message is: 

indexerror: list assignment index out of range.

To clarify, IndexError tells us that there is a problem with how we are accessing an index. An index is a value inside an iterable object, such as a list or a string. Then, the message “list assignment index out of range” tells us that we are trying to assign an item to an index that does not exist.

In order to use indexing on a list, you need to initialize the list. Moreover, if you try to assign an item into a list at an index position that does not exist, this error will be raised.

An Example Scenario

The list assignment error is commonly raised in for and while loops.

We’re going to write a program that adds all the cakes containing the word “Strawberry” into a new array. Let’s start by declaring two variables:

To clarify, the first variable stores our list of cakes. The second variable is an empty list that will store all of the strawberry cakes. Then, we’re going to write a loop that checks if each value in “cakes” contains the word “Strawberry”.

If a value contains “Strawberry”, it should be added to our new array. Otherwise, nothing will happen. Once our for loop has executed, the “strawberry” array should be printed to the console. Let’s run our code and see what happens:

As we expected, an error has been raised. Then, we get to solve it.

>>> Read more

• Local variable referenced before assignment: The UnboundLocalError in Python
• Rename files using Python: How to implement it with examples

The solution to list assignment Python index out of range

Our error message tells us the line of code at which our program fails:

To clarify, the problem with this code is that we are trying to assign a value inside our “strawberry” list to a position that does not exist.

When we create our strawberry array, it has no values. To clarify, this means that it has no index numbers. The following values do not exist:

We are trying to assign values to these positions in our for loop. Because these positions contain no values, an error is returned. So, we can solve this problem in two ways.

Solution with append()

Firstly, we can add an item to the “strawberry” array using append():

The  append()  method adds an item to an array and creates an index position for that item.

Let’s run our code:

The code works!

Solution with Initializing an Array to list assignment Python index out of range

Alternatively, we can initialize our array with some values when we declare it. Because, Tthis will create the index positions at which we can store values inside our “strawberry” array. Therefore, to initialize an array, you can use this code:

This will create an array with 10 empty values. Our code now looks like this:

Let’s try to run the code:

The code successfully returns an array with all the strawberry cakes.

This method is best to use when you know exactly how many values you’re going to store in an array.

The above code is somewhat inefficient because we have initialized “strawberry” with 10 empty values. There are only a total of three cakes in our “cakes” array that could possibly contain “Strawberry”.

To sum up with list assignment python index out of range

IndexErrors are raised when you try to use an item at an index value that does not exist. The “indexerror: list assignment index out of range” is raised when you try to assign an item to an index position that does not exist.

To solve this error, you can use  append()  to add an item to a list. You can also initialize a list before you start inserting values to avoid this error. So, now you’re ready to start solving the list assignment error like a professional Python developer .

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Indexerror: list Index Out of Range in Python

Updated Jun 22, 2021

Python List Index Out of Range

If you are working with lists in Python, you have to know the index of the list elements. This will help you access them and perform operations on them such as printing them or looping through the elements. But in case you mention an index in your code that is outside the range of the list, you will encounter an IndexError.

“ List index out of range ” error occurs in Python when we try to access an undefined element from the list.

The only way to avoid this error is to mention the indexes of list elements properly.

Example: 

In the above example, we have created a list named “ list_fruits ” with three values apple, banana, and orange. Here we are trying to print the value at the index [3] .

And we know that the index of a list starts from 0 that’s why in the list, the last index is 2 , not 3 . 

Due to which if we try to print the value at index [3] it will give an error.

Correct Example: 

Output: 

1. Example with "while" Loop

In the above case, the error occurs inline 5, as shown in output where print(list_fruits[i]) means that the value of “i” exceeds the index value of list “list_fruits.”

If you need to check why this error occurs, print the value of “i” just before “print(list_fruits[i])” statement.

print(list_fruits[i])

Example : 

In the above example output, we can see that the value of ‘i’ goes to “3” , whereas our list index is only up to 2.

Solution for this error 

2. Example with "for" Loop:

In the above example, we are printing the value at index 3, but the out list has indexed only up to 2.

To avoid such type of error, we have to run for loop in the range of “list” length.

We have seen the different situations where the list index out of range error might occur. You can check the length of the list using before performing operations or using the indexes.

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解决 Python 中IndexError: list assignment index out of range 错误

十年编程经验，定期分享Python干货，大家好我是 @迹忆客 关注我不迷路。

在 Python 中，当您尝试访问甚至不存在的列表的索引时，会引发 IndexError: list assignment index out of range 。 索引是可迭代对象（如字符串、列表或数组）中值的位置。

在本文中，我们将学习如何修复 Python 中的 Index Error list assignment index out-of-range 错误。

Python IndexError：列表分配索引超出范围

让我们看一个错误的例子来理解和解决它。

上面代码中 IndexError: list assignment index out of range 背后的原因是我们试图访问索引 3 处的值，这在列表 j 中不可用。

修复 Python 中的 IndexError: list assignment index out of range

要修复此错误，我们需要调整此案例列表中可迭代对象的索引。 假设我们有两个列表，你想用列表 b 替换列表 a。

您不能为列表 b 赋值，因为它的长度为 0，并且您试图在第 k 个索引 b[k] = I 处添加值，因此它会引发索引错误。 您可以使用 append() 和 insert() 修复它。

修复 IndexError: list assignment index out of range 使用 append() 函数

append() 函数在列表末尾添加项目（值、字符串、对象等）。 这很有帮助，因为您不必处理索引问题。

修复 IndexError: list assignment index out of range 使用 insert() 函数

insert() 函数可以直接将值插入到列表中的第 k 个位置。 它有两个参数， insert(index, value) 。

除了上述两种解决方案之外，如果你想像对待其他语言中的普通数组一样对待 Python 列表，你可以使用 None 值预定义你的列表大小。

一旦你用虚拟值 None 定义了你的列表，你就可以相应地使用它。

可能有更多的手动技术和逻辑来处理Python 中的 IndexError：list assignment index out of range 错误。 本文概述了两个常见的列表函数，它们可以帮助我们在替换两个列表时帮助我们处理 Python 中的索引错误。

我们还讨论了预定义列表并将其视为类似于其他编程语言数组的数组的替代解决方案。

码字不易，硬核码字更难，希望大家不要吝啬自己的鼓励。

Python에서 List Index Out of Range 오류 메세지 해결하기

Original article: List Index Out of Range – Python Error Message Solved

이 기사에서는 Python에서 리스트 인덱스가 범위를 벗어났다는 의미의 Indexerror: list index out of range 오류가 발생하는 몇 가지 이유에 대해 살펴보겠습니다.

오류가 발생하는 이유에 대해 알아본 후 이 오류를 방지하는 몇 가지 방법도 배워보겠습니다.

Python 리스트 생성하기

Python에서 리스트 객체를 생성하려면 다음을 실행해야 합니다.

• 리스트 객체의 이름을 지정하고,
• 할당 연산자인 = 를 사용하고,
• 대괄호 [] 안에 0개 이상의 리스트 항목을 포함합니다. 각 리스트 항목은 쉼표로 구분해야 합니다.

예를 들어, 이름 목록을 작성하려면 다음과 같은 코드를 실행합니다.

위의 코드는 Kelly, Nelly, Jimmy, Lenny 의 네 가지 값을 가진 names 라는 리스트를 생성합니다.

Python 리스트 길이 확인하기

리스트의 길이를 확인하려면 Python의 내장 함수 len() 를 사용하면 됩니다.

len() 은 리스트에 저장된 항목의 수인 정수를 반환합니다.

리스트에 저장된 항목이 4개이므로 리스트의 길이 또한 4입니다.

Python 리스트의 개별 항목에 접근하는 방법

리스트의 각 항목은 고유한 인덱스 번호(index number) 가 있습니다.

Python 및 대부분의 현대 프로그래밍 언어에서는 인덱싱이 0부터 시작합니다.

즉, 리스트의 첫 번째 항목은 0, 두 번째 항목은 1의 인덱스를 갖습니다.

인덱스를 활용해 개별 항목에 접근할 수 있습니다.

그러려면 먼저 리스트 이름을 작성합니다. 그런 다음 대괄호 안에 항목의 인덱스에 해당하는 정수를 포함합니다.

이전 예시의 경우 인덱스를 사용해 리스트 내의 각 항목에 접근하는 방법은 다음과 같습니다.

음수 인덱스(negative index)를 사용해 Python 리스트 내 항목에 접근할 수도 있습니다.

마지막 항목에 접근하려면 인덱스 값 -1을 사용하면 됩니다. 마지막에서 두 번째 항목에 접근하려면 인덱스 값 -2를 사용합니다.

다음 코드 블록은 음수 인덱스를 사용해 리스트 내의 각 항목에 접근하는 방법입니다.

Indexerror: list index out of range error 오류가 발생하는 이유

첫 번째 원인: 리스트 범위를 벗어나는 인덱스 사용.

리스트의 인덱스 범위를 벗어난, 존재하지 않는 값을 사용해 항목에 접근하려고 하면 Index error: list index out of range 오류가 발생합니다.

이 오류는 리스트의 마지막 항목에 접근하거나 음수 인덱스를 사용해 첫 번째 항목에 접근할 때 흔히 발생합니다.

예시를 다시 살펴봅시다.

리스트의 마지막 항목인 Lenny 에 접근하려고 다음과 같은 코드를 실행했다고 가정해봅시다.

일반적으로 리스트의 인덱스 범위는 0에서 n-1 이며, 여기서 n 은 리스트의 총 항목 수입니다.

예시의 names 리스트는 총 항목 수가 4 이고 인덱스 범위는 0에서 3 입니다.

이제 음수 인덱스로 리스트 항목을 접근해봅시다.

음수 인덱스를 사용해 첫 번째 항목인 Kelly 에 접근한다고 가정해볼까요?

음수 인덱스를 사용할 경우 리스트의 인덱스 범위는 -1에서 -n 입니다. 여기서 -n 은 리스트에 포함된 총 항목 수입니다.

리스트의 총 항목 수가 4 라면, 인덱스 범위는 -1에서-4 입니다.

두 번째 원인: for 문에서 range() 함수에 잘못된 값 전달

리스트를 순회할 때 존재하지 않는 항목에 접근하려고 하면 Indexerror: list index out of range 오류가 발생합니다.

이런 오류가 발생하는 흔한 경우 중 하나는 Python의 range() 함수에서 잘못된 정수를 사용했을 때입니다.

range() 함수에는 일반적으로 카운트가 종료하는 위치(종료값이라고도 불립니다 --옮긴이)를 나타내는 정수 하나가 전달됩니다.

예를 들어 range(5) 는 카운트가 0 에서 시작해 4 에서 종료됨을 나타냅니다.

다시 말해 카운트는 기본적으로 0 에서 시작되고 전달된 종료값에서 1을 뺀 값까지 매번 1 씩 증가합니다. range() 함수에 인자로 전달된 종료값은 카운트에 포함되지 않는다는 점을 꼭 명심하세요.

예시를 확인해봅시다.

names 리스트에는 네 가지 값이 있습니다.

이 리스트를 순회하고 각 항목의 값을 출력하고 싶다는 가정해보겠습니다.

range(5) 를 사용할 때 Python 인터프리터에게 0에서 4까지 에 위치한 값을 출력하라는 지시를 전하는 의미입니다.

그러나 4 위치에는 항목이 없습니다.

위치 번호를 출력한 후 해당 위치의 값을 출력해보면 이 사실을 확인할 수 있습니다.

range(5) 는 0에서 4까지 의 위치를 나타냅니다. 0 위치에는 "Kelly", 1 위치에는 "Nelly", 2 위치에는 "Jimmy", 그리고 3 위치에는 "Lenny"라는 값이 있다는 것을 확인할 수 있습니다.

4 위치의 경우 출력할 값이 없으므로 인터프리터가 오류를 발생시킵니다.

이 오류를 해결하는 한 가지 방법은 range() 에 전달된 정수를 낮추는 것입니다.

for 문을 사용할 때 이 오류를 해결하는 또 다른 방법은 리스트의 길이를 range() 함수에 인수로 전달하는 것입니다. 이전 섹션에서 설명한 것처럼 내장 함수 len() 를 사용하면 됩니다.

len() 을 range() 에 인수로 전달할 때 다음과 같은 실수를 조심하세요.

이런 코드를 실행하면 IndexError: list index out of range 오류가 다시 발생합니다.

이제 IndexError: list index out of range 오류가 발생하는 이유와 이를 방지할 수 있는 몇 가지 방법에 대해 이해가 잘 되셨나요?

Python에 대해 더 배워보고 싶다면 freeCodeCamp의 Python 수료증 과정 을 확인해보세요. 수료증 강의를 통해 초보자여도 Python을 재미있고 유익하게 배우면서 5개의 프로젝트를 해보며 배운 것을 열심히 실습할 수 있을 거에요.

읽어주셔서 감사합니다. Happy coding!

She/her | Software Engineer @ 100Devs | i read, i learn languages, i solve problems | 개발과 n개국어를 하는 사람 | ✝️🏳️‍🌈🐕

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