list assignment index out of range python significado

How to Fix the “List index out of range” Error in Python

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At many points in your Python programming career, you’re going to run into the “List index out of range” error while writing your programs. What does this mean, and how do we fix this error? We’ll answer that question in this article.

The short answer is: this error occurs when you’re trying to access an item outside of your list’s range. The long answer, on the other hand, is much more interesting. To get there, we’ll learn a lot about how lists work, how to index things the bad way and the good way, and finally how to solve the above-mentioned error.

This article is aimed at Python beginners who have little experience in programming. Understanding this error early will save you plenty of time down the road. If you’re looking for some learning material, our Python Basics track includes 3 interactive courses bundled together to get you on your feet.

Indexing Python Lists

Lists are one of the most useful data structures in Python. And they come with a whole bunch of useful methods . Other Python data structures include tuples, arrays, dictionaries, and sets, but we won’t go into their details here. For hands-on experience with these structures, we have a Python Data Structures in Practice course which is suitable for beginners.

A list can be created as follows:

Instead of using square brackets ([]) to define your list, you can also use the list() built-in function.

There are already a few interesting things to note about the above example. First, you can store any data type in a list, such as an integer, string, floating-point number, or even another list. Second, the elements don’t have to be unique: the integer 1 appears twice in the above example.

The elements in a list are indexed starting from 0. Therefore, to access the first element, do the following:

Our list contains 6 elements, which you can get using the len() built-in function. To access the last element of the list, you might naively try to do the following:

This is equivalent to print(x[len(x)]) . Since list indexing starts from 0, the last element has index len(x)–1 . When we try to access the index len(x) , we are outside the range of the list and get the error. A more robust way to get the final element of the list looks like this:

While this works, it’s not the most pythonic way. A better method exploits a nice feature of lists – namely, that they can be indexed from the end of the list by using a negative number as the index. The final element can be printed as follows:

The second last element can be accessed with the index -2, and so on. This means using the index -6 will get back to the first element. Taking it one step further:

Notice this asymmetry. The first error was trying to access the element after the last with the index 6, and the second error was trying to access the element before the first with the index -7. This is due to forward indexing starting at 0 (the start of the list), and backwards indexing starting at -1 (the end of the list). This is shown graphically below:

Looping Through Lists

Whenever you’re working with lists, you’ll need to know about loops. A loop allows you to iterate through all the elements in a list.

The first type of loop we’ll take a look at is the while loop. You have to be a little more careful with while loops, because a small mistake will make them run forever, requiring you to force the program to quit. Once again, let’s try to naively loop through our list:

In this example we define our index, i , to start from zero. After every iteration of our while loop, we print the list element and then go to the next index with the += assignment operator. (This is a neat little trick, which is like doing i=i+1 .)

By the way, if you forget the final line, you’ll get an infinite loop.

We encountered the index error for the same reason as in the first section – the final element has index len(x)-1 . Just modify the condition of the while statement to reflect this, and it will work without problems.

Most of your looping will be done with a for loop, which we’ll now turn our attention to. A better method to loop through the elements in our list without the risk of running into the index error is to take advantage of the range() built-in function. This takes three arguments, of which only the stop argument is required. Try the following:

The combination of the range() and len() built-in functions takes care of worrying about when to stop indexing our list to avoid the index out of range error entirely. This method, however, is only useful if you care about knowing what the index is.

For example, maybe you want to print out the index and the element. In that case, all you need to do is modify the print() statement to print(i, x[i]) . Try doing this for yourself to see the result. Alternatively, you can use The enumerate() function in Python.

If you just want to get the element, there’s a simpler way that’s much more intuitive and readable. Just loop through the elements of the list directly:

If the user inputs an index outside the range of the list (e.g. 6), they’ll run into the list index error again. We can modify the function to check the input value with an if statement:

Doing this prevents our program from crashing if the index is out of range. You can even use a negative index in the above function.

There are other ways to do error handling in Python that will help you avoid errors like “list index out of range”. For example, you could implement a try-exceptaa block instead of the if-else statement.

To see a try-except block in action, let’s handle a potential index error in the get_value() function we wrote above. Preventing the error looks like this:

As you can probably see, the second method is a little more concise and readable. It’s also less error-prone than explicitly checking the input index with an if-else statement.

Master the “List index out of range” Error in Python

You should now know what the index out of range error in Python means, why it pops up, and how to prevent it in your Python programs.

A useful way to debug this error and understand how your programs are running is simply to print the index and compare it to the length of your list.

This error could also occur when iterating over other data structures, such as arrays, tuples, or even when iterating through a string. Using strings is a little different from  using lists; if you want to learn the tools to master this topic, consider taking our Working with Strings in Python course. The skills you learnt here should be applicable to many common use cases.

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

Table of Contents

The IndexError: List Assignment Index Out of Range error occurs when you assign a value to an index that is beyond the valid range of indices in the list. As Python uses zero-based indexing, when you try to access an element at an index less than 0 or greater than or equal to the list’s length, you trigger this error.

It’s not as complicated as it sounds. Think of it this way: you have a row of ten mailboxes, numbered from 0 to 9. These mailboxes represent the list in Python. Now, if you try to put a letter into mailbox number 10, which doesn't exist, you'll face a problem. Similarly, if you try to put a letter into any negative number mailbox, you'll face the same issue because those mailboxes don't exist either.

The IndexError: List Assignment Index Out of Range error in Python is like trying to put a letter into a mailbox that doesn't exist in our row of mailboxes. Just as you can't access a non-existent mailbox, you can't assign a value to an index in a list that doesn't exist.

Let’s take a look at example code that raises this error and some strategies to prevent it from occurring in the first place.

Example of “IndexError: List Assignment Index Out of Range”

Remember, assigning a value at an index that is negative or out of bounds of the valid range of indices of the list raises the error.

How to resolve “IndexError: List Assignment Index Out of Range”

You can use methods such as append() or insert() to insert a new element into the list.

How to use the append() method

Use the append() method to add elements to extend the list properly and avoid out-of-range assignments.

How to use the insert() method

Use the insert() method to insert elements at a specific position instead of direct assignment to avoid out-of-range assignments.

Now one big advantage of using insert() is even if you specify an index position which is way out of range it won’t give any error and it will just append the element at the end of the list.

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How to fix IndexError: list assignment index out of range in Python

This tutorial will show you an example that causes this error and how to fix it in practice

How to reproduce this error

Because the list has two items, the index number ranges from 0 to 1. Assigning a value to any other index number will cause this error.

How to fix this error

Take your skills to the next level ⚡️.

Comprehensive Guide to Solving IndexError List Assignment Index Out of Range in Python

Dealing with the "IndexError: list assignment index out of range" can be one of the most frustrating parts of working with Python‘s powerful and flexible lists. In this detailed guide, we‘ll dig deep into the causes of index errors and multiple effective strategies to avoid them.

Whether you‘re a beginner looking to understand this common exception or an experienced Pythonista hoping to master list indexing best practices, read on for the definitive guide to solving index out of range errors for good!

What Exactly is an IndexError?

Let‘s start by looking at a simple example that demonstrates how this error occurs:

Attempting to run this code produces the familiar IndexError:

This error means we are trying to access or assign a value at an index that is larger than the length of the list.

In Python, lists are 0-indexed – the first element is at index 0, the second at 1, and so on. For our list of length 3, the last valid index is 2. By trying to assign a value at index 3, we‘ve gone out of range, resulting in the index error.

This error frequently occurs when trying to append to an existing list by directly accessing indexes. Without caution, it‘s easy to go past the end of the intended list.

According to Python‘s bug tracker, IndexError is one of the most common exceptions in Python code. Let‘s explore why these errors occur and how to avoid them.

Why Index Errors Happen

There are two main reasons why the IndexError occurs:

1. Accessing an out of range index

This occurs when trying to access or assign a value at a list index that is greater than or equal to the length of the list:

2. Changing list size while iterating

This can happen when iterating through a list while also appending or removing elements from it:

The append() inside the loop continues extending the list, going past the original indexes.

Understanding these two scenarios is key to avoiding accidental index errors down the line.

Frequency of IndexError

According to data from Python‘s bug tracker on Github, IndexError is one of the most common exceptions in Python code:

It accounts for over 15% of all Python exceptions. This demonstrates how often developers unintentionally go out of bounds with list indexing.

The frequency is even higher for data analysts and scientists working with Python and numerical data structures like matrices and ndarrays. So this is an essential error to know how to handle properly.

Below we dig into several effective ways to solve the problem.

Checking Length with len()

One way to avoid index errors is to check the length of the list before trying to access any indexes.

Python‘s built-in len() function returns the length of a given list:

We can use len() to verify an index is within the valid range before accessing it:

Here we safely check that index 3 is less than the length before attempting assignment. If the test fails, we avoid the error and can print a custom message.

Checking lengths is a simple way to avoid index errors, especially when accepting user input that may contain arbitrary indexes.

Leveraging append() and insert()

Rather than directly accessing indexes, we can use the append() and insert() methods available on Python lists.

append() will add the element to the end of the list:

No need to worry about the index, it takes care of appending for us!

insert() allows specifying the index to insert before:

This allows inserting items at any valid index, rather than relying on manual assignments.

Both append() and insert() protect us from index errors by handling the indexes internally.

Catching the Exception

In situations where we need direct access to indexes, we can handle potential errors using try/except:

This catches the IndexError exception and allows us to print a custom error message instead of the usual ugly stack trace.

Exception handling is useful when accessing indexes in a loop or working with matrices using multiple dimensions. We can elegantly continue execution after catching any out of range errors.

Extending vs Appending for Performance

When adding multiple items to a list, using list.extend() is preferred over repeated append() calls:

extend() iterates over the given iterable, appending each item individually. This is faster than individual append() calls and protects us from potential off-by-one index errors.

Under the hood, extend() actually calls the lower level list.append() method as it loops. But by handling the iteration for us, we avoid mistakes.

Relationship to Key Errors

It‘s worth noting the relationship between IndexError and KeyError – two very common errors.

IndexError refers specifically to invalid indexes on sequences like lists. KeyError refers to invalid keys for dict objects.

For example:

Both indicate an attempt to access missing values in a data structure. The main difference is KeyError applies to dicts rather than sequences.

Best Practices for Avoiding Index Errors

Now that we‘ve explored various solutions, let‘s look at some best practices for avoiding index errors:

• Use len() to validate indexes before accessing
• Prefer append() and insert() over direct access
• Handle exceptions gracefully with try/except
• Know the difference between extend() and append()
• Be careful modifying lists while iterating over them
• Consider reserving list size if known in advance with .append(None)
• Access indexes relatively with negative values (-1 for last)
• Iterate with enumerate() and access indexes safely

Following these guidelines will help you ditch frustrating index errors in Python for good!

Comparison to Indexing in Other Languages

It‘s interesting to compare Python‘s list indexing and errors to other popular languages:

• JavaScript : Allows access past end without errors (undefined returned)
• C++ : Out of range access leads to undefined behavior
• Java : Throws IndexOutOfBoundsException rather than IndexError
• R : Vector and matrix indexes start at 1 rather than 0

So this behavior is unique to Python‘s zero-based indexing approach combined with dynamic types. Knowing how other languages handle indexing differently can help avoid errors when switching between languages.

To recap, the IndexError occurs when trying to access or assign values at a list index that is out of the valid range. By leveraging length checks, append/insert methods, exception handling, and preferred idioms like extend, you can access list elements safely and avoid "index out of range" headaches.

Now that you have a comprehensive understanding of this common exception, you can squash frustrating index errors in your Python code for good!

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Python indexerror: list assignment index out of range Solution

An IndexError is nothing to worry about. It’s an error that is raised when you try to access an index that is outside of the size of a list. How do you solve this issue? Where can it be raised?

In this article, we’re going to answer those questions. We will discuss what IndexErrors are and how you can solve the “list assignment index out of range” error. We’ll walk through an example to help you see exactly what causes this error.

Find your bootcamp match

Without further ado, let’s begin!

The Problem: indexerror: list assignment index out of range

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

Our error message is: indexerror: list assignment index out of range.

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.

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. 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:

The first variable stores our list of cakes. The second variable is an empty list that will store all of the strawberry cakes. Next, 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. Now we get to solve it!

The Solution

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

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. 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.

We can solve this problem in two ways.

Solution with append()

First, 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: [‘Strawberry Tart’, ‘Strawberry Cheesecake’].

Our code works!

Solution with Initializing an Array

Alternatively, we can initialize our array with some values when we declare it. This will create the index positions at which we can store values inside our “strawberry” array.

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 our code:

Our 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.

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Our 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”. In most cases, using the append() method is both more elegant and more efficient.

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.

Now you’re ready to start solving the list assignment error like a professional Python developer!

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List Index Out of Range – Python Error Message Solved

In this article you'll see a few of the reasons that cause the list index out of range Python error.

Besides knowing why this error occurs in the first place, you'll also learn some ways to avoid it.

Let's get started!

How to Create a List in Python

To create a list object in Python, you need to:

• Give the list a name,
• Use the assignment operator, = ,
• and include 0 or more list items inside square brackets, [] . Each list item needs to be separated by a comma.

For example, to create a list of names you would do the following:

The code above created a list called names that has four values: Kelly, Nelly, Jimmy, Lenny .

How to Check the Length of a List in Python

To check the length of a list in Python, use Python's build-in len() method.

len() will return an integer, which will be the number of items stored in the list.

There are four items stored in the list, therefore the length of the list will be four.

How to Access Individual List Items in Python

Each item in a list has its own index number .

Indexing in Python, and most modern programming languages, starts at 0.

This means that the first item in a list has an index of 0, the second item has an index of 1, and so on.

You can use the index number to access the individual item.

To access an item in a list using its index number, first write the name of the list. Then, inside square brackets, include the intiger that corresponds with the item's index number.

Taking the example from earlier, this is how you would access each item inside the list using its index number:

You can also use negative indexing to access items inside lists in Python.

To access the last item, you use the index value of -1. To acces the second to last item, you use the index value of -2.

Here is how you would access each item inside a list using negative indexing:

Why does the Indexerror: list index out of range error occur in Python?

Using an index number that is out of the range of the list.

You'll get the Indexerror: list index out of range error when you try and access an item using a value that is out of the index range of the list and does not exist.

This is quite common when you try to access the last item of a list, or the first one if you're using negative indexing.

Let's go back to the list we've used so far.

Say I want to access the last item, "Lenny", and try to do so by using the following code:

Generally, the index range of a list is 0 to n-1 , with n being the total number of values in the list.

With the total values of the list above being 4 , the index range is 0 to 3 .

Now, let's try to access an item using negative indexing.

Say I want to access the first item in the list, "Kelly", by using negative indexing.

When using negative indexing, the index range of a list is -1 to -n , where -n the total number of items contained in the list.

With the total number of items in the list being 4 , the index range is -1 to -4 .

Using the wrong value in the range() function in a Python for loop

You'll get the Indexerror: list index out of range error when iterating through a list and trying to access an item that doesn't exist.

One common instance where this can occur is when you use the wrong integer in Python's range() function.

The range() function typically takes in one integer number, which indicates where the counting will stop.

For example, range(5) indicates that the counting will start from 0 and end at 4 .

So, by default, the counting starts at position 0 , is incremented by 1 each time, and the number is up to – but not including – the position where the counting will stop.

Let's take the following example:

Here, the list names has four values.

I wanted to loop through the list and print out each value.

When I used range(5) I was telling the Python interpreter to print the values that are at the positions 0 to 4 .

However, there is no item in position 4.

You can see this by first printing out the number of the position and then the value at that position.

You see that at position 0 is "Kelly", at position 1 is "Nelly", at position 2 is "Jimmy" and at position 3 is "Lenny".

When it comes to position four, which was specified with range(5) which indicates positions of 0 to 4 , there is nothing to print out and therefore the interpreter throws an error.

One way to fix this is to lower the integer in range() :

Another way to fix this when using a for loop is to pass the length of the list as an argument to the range() function. You do this by using the len() built-in Python function, as shown in an earlier section:

When passing len() as an argument to range() , make sure that you don't make the following mistake:

After running the code, you'll again get an IndexError: list index out of range error:

Hopefully this article gave you some insight into why the IndexError: list index out of range error occurs and some ways you can avoid it.

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IndexError: list index out of range and python

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Why does this occur?

We see this error when indexing a list while using a value outside the range of indexes for the list. Today we'll take a look at some of the most common causes of this error, along with how to solve it using some practical examples.

Cause 1: Indexing the Final List Value

This problem frequently occurs when trying to index the end of a list.

Let's say you've got a list of ten values, but you're only interested in getting the final value in the list. We could do this as shown below:

Recall that indexing in Python starts at zero . We're getting this error because we've gone outside the range of the list. Even though the list has a length of ten, its indexes only range from 0-9, making the tenth index out of range.

We can fix the error by altering the index used to return the final list value, shown in the following solution:

Now that the index is within the correct range, the code runs successfully.

An alternative way of returning list values is to use a negative index. See below for an image showing the negative indexes of example_list , followed by a solution that uses a negative index to return the final list value:

Cause 2: Altering List while Looping

Another common cause of this error is modifying a list while looping over it. Generally, you should rarely change a data structure while looping over it.

Let's say you've got a list of colors called colors . You're not a big fan of the color blue, so you'd like to remove all blue values from the list. We can attempt this as shown below:

This error occurs because the del command changes the list length while in the loop.

At the start of the for loop, the length of colors is five, so the range() function generates the list [0, 1, 2, 3, 4] .

Although our list length decreases every time we delete an item, the range list we are looping through will remain the same. We'll eventually run into the index error in the later stages of our for loop since range() will be providing indexes greater than the length of the list.

To avoid editing the list directly while looping over it, we utilize list comprehension .

In just one line of code, we can remove any blue values from colors .

List comprehension works by creating a new list (as denoted by the brackets), then utilizing a for to iterate through all values in the list. The addition of if color != 'blue' communicates to Python that we're only interested in values that aren't blue, storing these in a new list. Once the for loop has finished iterating through all of the list values, we replace the old list.

This index error is triggered when indexing a list using a value outside of its range of indexes. The best way to avoid it is by carefully considering what range of indexes a list might have, taking into account that list indexes start at zero instead of one. As we've discussed, it's also a good idea to avoid editing a list while iterating over it, which can cause many issues.

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How to solve indexerror: list assignment index out of range

In this article, you will learn how to solve  indexerror: list assignment index out of range  Python error.

Let’s look at a code example that produces the same error.

In order to solve indexerror: list assignment index out of range Python error you need to  use  append()  to add an item to a list. consider the code example below:

This guide is part of the “ Common Python Errors ” series. It’s focused entirely on providing quick and easy solutions for Python-related problems.

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How to Fix Python IndexError: list assignment index out of range

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Python IndexError: list assignment index out of range

Fix the indexerror: list assignment index out of range in python, fix indexerror: list assignment index out of range using append() function, fix indexerror: list assignment index out of range using insert() function.

In Python, the IndexError: list assignment index out of range is raised when you try to access an index of a list that doesn’t even exist. An index is the location of values inside an iterable such as a string, list, or array.

In this article, we’ll learn how to fix the Index Error list assignment index out-of-range error in Python.

Let’s see an example of the error to understand and solve it.

Code Example:

The reason behind the IndexError: list assignment index out of range in the above code is that we’re trying to access the value at the index 3 , which is not available in list j .

To fix this error, we need to adjust the indexing of iterables in this case list. Let’s say we have two lists, and you want to replace list a with list b .

You cannot assign values to list b because the length of it is 0 , and you are trying to add values at kth index b[k] = I , so it is raising the Index Error. You can fix it using the append() and insert() .

The append() function adds items (values, strings, objects, etc.) at the end of the list. It is helpful because you don’t have to manage the index headache.

The insert() function can directly insert values to the k'th position in the list. It takes two arguments, insert(index, value) .

In addition to the above two solutions, if you want to treat Python lists like normal arrays in other languages, you can pre-defined your list size with None values.

Once you have defined your list with dummy values None , you can use it accordingly.

There could be a few more manual techniques and logic to handle the IndexError: list assignment index out of range in Python. This article overviews the two common list functions that help us handle the Index Error in Python while replacing two lists.

We have also discussed an alternative solution to pre-defined the list and treat it as an array similar to the arrays of other programming languages.

Zeeshan is a detail oriented software engineer that helps companies and individuals make their lives and easier with software solutions.

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Python indexerror: list assignment index out of range Solution

Posted in PROGRAMMING LANGUAGE /   PYTHON

Vinay Khatri Last updated on September 18, 2024

Table of Content

IndexError is one of the most common errors that arise when we try to use an index value out of the range of a string, list, or tuple. This error will not give you a hard time if you know how this error raises and how to debug it.

In this Python tutorial, we will discuss the " list assignment index out of range " error which is a Python IndexError tutorial. By the end of this tutorial, you will have a complete idea about this error and how to solve it. So let's get started with the error.

The Problem: IndexError: list assignment index out of range

The error statement is divided into two parts the Error Type and the Error Message.

• Error Type ( IndexError ) : This error raises when we try to use an index value that is out of the iterator range.
• Error Message ( list assignment index out of range ): This error message is telling us that we are trying to assign a new element to that index value that does not exist in the list.

Analyze Output

We are getting this error because our list my_list contain only 3 elements, which make it index range from 0 to 2 . But in line 4, we are assigning the new value 'd' at my_list index 3 , that does not exist. That's why the Python interpreter threw IndexError: list assignment index out of range error.

The very straightforward solution to solve this problem is using the Python append() method. The append method adds the new element at the end of the list. Because at last, we are getting this error because we are trying to access that list index that is out of the listed range. The append method will help us to add a new element by adding them at the end of the list.

Let's solve the above example using the append method

In this Python tutorial, we learned what is IndexError: list assignment index out of range” error in Python, and how to debug it using the Python list append method. Every time you see an index error in your Python shell, the first thing that should pop into your mind is that you are using an out-of-range index number.

A little bit of logic and error handling practice in Python will teach you how to solve this and all the other common errors in Python.

If you are still getting this error in your Python program, feel free to comment your code and query in the comment section. We will try to help you in debugging.

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Vinay Khatri I am a Full Stack Developer with a Bachelor's Degree in Computer Science, who also loves to write technical articles that can help fellow developers.

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How to Fix list assignment index out of range in Python

Learn what causes IndexError: list assignment index out of range errors in Python and how to avoid and fix them by using valid indexes and methods like len(), append(), and insert().

One of the most common errors that Python programmers encounter is the IndexError: list assignment index out of range. This error occurs when you try to assign a value to an index that does not exist in a list. In this article, we will explain what causes this error, how to avoid it, and how to fix it if it happens.

What is a list assignment index out of range error?

A list is a data structure that stores multiple values in a single variable. You can access the values in a list by using their index, which is a number that represents their position in the list. The first value in a list has an index of 0, the second value has an index of 1, and so on.

For example, consider the following list:

You can access the first value in the list by using fruits[0] , which returns "apple" . You can also assign a new value to an existing index by using the same syntax. For example, you can change the second value in the list by using fruits[1] = "pear" , which updates the list to ["apple", "pear", "orange"] .

However, if you try to assign a value to an index that is out of range, meaning that it is either negative or greater than or equal to the length of the list, you will get an IndexError: list assignment index out of range. For example, if you try to assign a value to fruits[3] , you will get an error because the list only has three values, and the valid indexes are 0, 1, and 2.

How to avoid list assignment index out of range errors?

There are two main ways to avoid list assignment index out of range errors:

• Check the length of the list before assigning a value to an index. You can use the len() function to get the number of values in a list. For example, if you want to assign a value to the last index in a list, you can use len(list) - 1 as the index. For example:
• Use the append() method to add a new value to the end of the list. This method automatically increases the length of the list and assigns the new value to the last index. For example:

How to fix list assignment index out of range errors?

If you encounter a list assignment index out of range error, you need to identify which line of code caused the error and what index you tried to assign a value to. Then, you need to either adjust the index to be within the valid range or use another method to add a new value to the list.

For example, suppose you have the following code that tries to create a new list by adding one to each value in another list:

This code will raise an IndexError: list assignment index out of range because new_numbers is an empty list and has no indexes. To fix this error , you can use the append() method instead of indexing:

Alternatively, you can initialize new_numbers with the same length as numbers and fill it with zeros or None values:

In this article, we learned what causes IndexError: list assignment index out of range errors in Python and how to avoid and fix them. We learned that we need to make sure that we use valid indexes when assigning values to lists and that we can use methods like len() , append() , and insert() to manipulate lists without causing errors.

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