In this tutorial, you’ll learn how to use Python to reverse a list. This is a common task at hand (and a common Python interview question you’ll encounter). Knowing how to approach this task in different ways can help you choose the right method in different situations. Show
Python comes with a number of methods and functions that allow you to reverse a list, either directly or by iterating over the list object. You’ll learn how to reverse a Python list by using
the While learning six different methods to reverse a list in Python may seem excessive, one of the beautiful things about Python is the flexibility it affords. Some methods will fit better into your style, while others may be more performant or easier to read. Let’s get started! The Quick Answer: Use a Python’s
Summary: How to Reverse a List in PythonIn this guide, we’ll cover six different ways of reversing a list in Python. However, let’s cover what the best and fastest way to reverse a list in Python is. From there, you can read about the various methods in the sections below. The most Pythonic way to reverse a list is to use the The fastest way to reverse a list in Python is to use either a for loop or a list comprehension. In order to test this, we tested each method on a list containing 100,000,000 items! This allowed us to really stress test each of the different methods. Let’s take a look at what the results were for each of the methods:
Now that we’ve covered that, let’s dive into how to use these different methods to reverse a list in Python. Understanding Python List IndexingBefore we dive into how to reverse a Python list, it’s important for us to understand how Python lists are indexed. Because Python lists are ordered and indexed, we can access and modify Python lists based on their index. Python list indices work in two main ways:
The image below demonstrates how list items can be indexed. How Python list indexing worksIn the next section, you’ll learn how to use the Python list Reverse a Python List Using the reverse methodPython lists have access to a method, Let’s see how we can reverse our Python list using the
Because the operation is handled in place, if you need to retain the original list, you’ll first need to create a copy of it. We can create
a copy of the list by using the
We can see that by first applying the In the next section, you’ll learn how to reverse a list by using list indexing. Reverse a Python List Using the reversed functionPython has a built-in function, The Let’s take a look at how we can use the
The We can verify this by writing the following code:
By passing the object into the At its core, the iterator object is quite memory efficient. This is because it behaves like a generator object and evaluates lazily (only when an item is accessed). When we convert it to a list using the In the following section, you’ll learn how to use list indexing to reverse a Python list. Reverse a Python List Using List IndexingWhen indexing a list, people generally think of accessing all items between a start and an end position. However, you can also include a For example, Moving over a list from end to the beginning is the same as reversing it. Let’s see how we can use Python’s list indexing to reverse a list:
In the code above, we create a new list by stepping over the original list in reverse order. This method doesn’t modify the object in place and needs to be assigned to a variable. Reverse a Python List Using a For LoopPython for loops are great ways to repeat an action for a defined number of times. We can use the reversed() and iterate over its items to create a list in reverse order. Let’s see how this can be done:
Let’s break down what the code block above is doing:
In the next section, you’ll learn how to use a Python list comprehension in order to reverse a list. Reverse a Python List Using a List ComprehensionSimilar to using a for loop for this, we can also use a list comprehension to reverse a Python list. Rather than simply converting the for loop to a list comprehension, however, we’ll use a slightly different approach to accomplish our goal. We will iterate over each item in our original list in the negative order. Let’s take a look at what this looks like:
Let’s break down what the code above is doing:
This method works, but it’s not the most readable method. It can be a good way to learn how to do this for an interview, but beyond this, it’s not the most recommended method. Reverse a Python List Using the Slice MethodPython also provides a Let’s see how we can use the function in Python:
The benefit of this approach is that we can assign a custom slice that can be easily re-used, without needing to modify multiple items. This allows you to easily apply the same slice to multiple items. In addition to this, the Frequently Asked QuestionsWhat is the best way to reverse a list in Python? The best and most Pythonic way to reverse a list in Python is to use the How do you reverse a list in Python using slicing? The best way to reverse a list
using slicing in Python is to use negative indexing. This allows you to step over a list using -1, by using the code What is the fastest way to reverse a list in Python? The fastest way to reverse a list in Python is to use a for loop (or a list comprehension). This method is hundreds of times faster than other methods (even when tested against lists with 100,000,000 items). ConclusionIn this tutorial, you learned how to reverse a list in Python. You learned how list indexing works and how this can be used to reverse a list. You then learned how to use the Additional ResourcesTo learn more about related topics, check out the tutorials below:
How do you reverse a list in Python without reverse function?In order to reverse a list without using the built-in reverse() function, we use the Slicing Operator. The slicing operator is another method used for reversing the data elements.
How do you manually reverse a list in Python?Reversing a list using the reversed() and reverse() built-in function. Using reversed() we can reverse the list and a list_reverseiterator object is created, from which we can create a list using list() type casting. Or, we can also use list. reverse() function to reverse list in-place.
What is the easiest way to reverse a list in Python?In Python, there is a built-in function called reverse() that is used to revers the list. This is a simple and quick way to reverse a list that requires little memory. Syntax- list_name. reverse() Here, list_name means you have to write the name of the list which have to be reversed.
How do you reverse a list by slicing?To reverse a list in Python, you can use negative slicing: As you want to slice the whole list, you can omit the start and stop values altogether. To reverse the slicing, specify a negative step value. As you want to include each value in the reversed list, the step size should be -1.
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