How to replace elements in list python

Python: Replace Item in List (6 Different Ways)

In this tutorial, you’ll learn how to use Python to replace an item or items in a list. You’l learn how to replace an item at a particular index, how to replace a particular value, how to replace multiple values, and how to replace multiple values with multiple values.

Being able to work with lists is an important skill for any Python developer, given how prevalent and understandable these Python data structures are.

By the end of this tutorial, you’ll have learned:

Table of Contents

Replace an Item in a Python List at a Particular Index

Python lists are ordered, meaning that we can access (and modify) items when we know their index position. Python list indices start at 0 and go all the way to the length of the list minus 1.

If we want to replace a list item at a particular index, we can simply directly assign new values to those indices.

Let’s take a look at what that looks like:

In the next section, you’ll learn how to replace a particular value in a Python list using a for loop.

Want to learn how to use the Python zip() function to iterate over two lists? This tutorial teaches you exactly what the zip() function does and shows you some creative ways to use the function.

Replace a Particular Value in a List in Python Using a For Loop

Python lists allow us to easily also modify particular values. One way that we can do this is by using a for loop.

One of the key attributes of Python lists is that they can contain duplicate values. Because of this, we can loop over each item in the list and check its value. If the value is one we want to replace, then we replace it.

Let’s see what this looks like. In our list, the word apple is misspelled. We want to replace the misspelled version with the corrected version.

Let’s take a look at what we’ve done here:

In the next section, you’ll learn how to turn this for loop into a Python list comprehension.

Want to learn more about Python for-loops? Check out my in-depth tutorial that takes your from beginner to advanced for-loops user! Want to watch a video instead? Check out my YouTube tutorial here.

Replace a Particular Value in a List in Python Using a List Comprehension

One of the key attributes of Python list comprehensions is that we can often turn for loops into much shorter comprehensions. Let’s see how we can use a list comprehension in Python to replace an item in a list.

We’ll use the same example we used in the for loop, to help demonstrate how elegant a Python list comprehension can be:

We can see here that there are two main benefits of list comprehensions compared to for loops:

In the next section, you’ll learn how to change all values in a list using a formula.

Want to learn more about Python list comprehensions? Check out this in-depth tutorial that covers off everything you need to know, with hands-on examples. More of a visual learner, check out my YouTube tutorial here.

Change All Values in a List in Python Using a Function

Neither of the approaches above are immediately clear as to what they are doing. Because of this, developing a formula to do this is a helpful approach to help readers of your code understand what it is you’re doing.

Let’s take a look at how we can use the list comprehension approach and turn it into a formula:

Here, we simply need to pass in the list, the item we want to replace, and the item we want to replace it with. The function name makes it easy to understand what we’re doing, guiding our readers to better understand our actions.

In the next section, you’ll learn how to replace multiple values in a Python list.

Replace Multiple Values in a Python List

There may be many times when you want to replace not just a single item, but multiple items. This can be done quite simply using the for loop method shown earlier.

Similar to the for loop method shown earlier, we check whether or not an item is a typo or not and replace its value.

In the next section, you’ll learn how to replace multiple values in a Python list with different values.

Replace Multiple Values with Multiple Values in a Python List

The approach above is helpful if we want to replace multiple values with the same value. There may be times where you want to replace multiple values with different values.

Looking again at our example, we may want to replace all instances of our typos with their corrected spelling. We can again use a for loop to illustrate how to do this.

Instead of using a single if statement, we’ll nest in some elif statements that check for a value’s value before replacing.

Need to check if a key exists in a Python dictionary? Check out this tutorial, which teaches you five different ways of seeing if a key exists in a Python dictionary, including how to return a default value.

Conclusion

In this tutorial, you learned how to use Python to replace items in a list. You learned how to use Python to replace an item at a particular index, how to replace a particular value, how to modify all values in a list, and how to replace multiple values in a list.

To learn more about Python list indexing, check out the official documentation here.

Additional Resources

To learn more about related topics, check out the tutorials below:

7 Efficient Ways to Replace Item in List in Python

Lists in python are data structures used to store items of multiple types together under the same list. Using a list, we can store several data types such as string values, integer, float, sets, nested lists, etc. The items are stored inside square brackets ‘[ ]’. They are mutable data types, i.e., they can be changed even after they have been created. We can access list elements using indexing. In this article, we shall look into 7 efficient ways to replace items in a python list.

How to replace item in list python

Lists are compelling and versatile data structures. As mentioned above, lists are mutable data types. Even after a list has been created, we can make changes in the list items. This property of lists makes them very easy to work with. Here, we shall be looking into 7 different ways in order to replace item in a list in python.

1. Using list indexing

The list elements can be easily accessed with the help of indexing. This is the most basic and the easiest method of accessing list elements. Since all the elements inside a list are stored in an ordered fashion, we can sequentially retrieve its elements. The first element is stored at index 0, and the last element is stored at index ‘len(list)-1’.

Let us take a list named ‘my_list’, which stores names of colors. Now, if we want to replace the first item inside the list from ‘Red’ to ‘Black’, we can do that using indexing. We assign the element stored at the 0th index to a new value. Then the list printed would contain the replaced item.

2. Looping using for loop

We can also execute a for loop to iterate over the list items. When a certain condition is fulfilled inside the for loop, we will then replace that list item using indexing.

We shall take the same ‘my_list’ as in the above example. Then, we shall run the for loop for the length of the list ‘my_list’. Inside the loop, we have placed the condition that when the list element equals ‘Orange’, we will replace the item at that index with ‘Black’. Then after the for loop ends, we shall print that list.

The output prints the list with the replaced value.

3. Using list comprehension

List Comprehension in python is a compact piece of code. Using list comprehension, we can generate new sequences from already existing sequences. Instead of writing an entire block of code for executing a for loop or an if-else loop, we can write a single line code for the same.

The syntax for list comprehension is:

It consists of the expression which has to be printed into the new list, the loop statement, and the original list from which the new values will be obtained.

We shall use list comprehension to append the string ‘ color’ to all the list elements of my_list. We shall replace the old values with the updated values.

The list with replaced values is:

4. With map and lambda function

Map() is a built-in function in python using which we can iterate over an iterable sequence without having to write a loop statement.

The syntax of the map is:

Here, every value inside the iterable will be passed into a function, and the map() function will output the inside function’s return value. Inside the map() function, we have taken a lambda function as the first argument.

A lambda function is an anonymous function containing a single line expression. It can have any number of arguments, but only one expression can be evaluated. Here, the lambda function will append the string ‘ color’ for all the items present in the list and return the new value. Then using the list() function, we shall convert the map object returned by the map() function into a list.

The output is:

If we want to replace a particular item in the list, then the code for that will be:

We have used the replace() method to replace the value ‘Orange’ from my_list to ‘Black.’ The output is:

5. Executing a while loop

We can also have a while loop in order to replace item in a list in python. We shall take a variable ‘i’ which will be initially set to zero. The while loop shall execute while the value of ‘i’ is less than the length of the list my_list. We shall use the replace() method to replace the list item ‘Gray’ with ‘Green.’ The variable ‘i’ shall be incremented at the end of the loop.

The updated list is:

6. Using list slicing

We can also perform slicing inside a list. Using slicing enables us to access only a certain part of a list.

The syntax of the list is:

Using list slicing, we can replace a given item inside a list. First, we shall store the index of the item to be replaced into a variable named ‘index.’ Then, using list slicing, we will replace that item with a new value, ‘Green.’

The output is:

7. Replacing list item using numpy

We can also replace a list item using python’s numpy library. First, we will convert the list into a numpy array. Then using numpy’s where() function, we specify a condition according to which we will replace the value. We shall replace the value ‘Gray’ with ‘Green.’ Else, the value will be the same.

The output is:

FAQ’s Related to Replace item in list in Python

Using list comprehension, map-lambda function, replace function, etc., we can perform in-place replacement of list items.

This sums up five different ways of replacing an item in a list. If you have any questions in your mind, then let us know in the comments below.

Replace Item in List in Python: A Complete Guide

There are three ways to replace an item in a Python list. You can use list indexing or a for loop to replace an item. If you want to create a new list based on an existing list and make a change, you can use a list comprehension.

You may decide that you want to change a value in a list. Suppose you’re building a menu for a restaurant. You may notice that you have misspelled one of the menu items. To fix this mistake, you will need to change an existing element in the list.

Python Replace Item in List

You can replace an item in a Python list using a for loop, list indexing, or a list comprehension. The first two methods modify an existing list whereas a list comprehension creates a new list with the specified changes.

Let’s summarize each method:

In this guide, we walk through each of these methods. We’ll refer to an example of each to help you get started.

Python Replace Item in List: Using List Indexing

The easiest way to replace an item in a list is to use the Python indexing syntax. Indexing allows you to choose an element or range of elements in a list. With the assignment operator, you can change a value at a given position in a list.

Let’s start by creating a list which contains our product prices:

81% of participants stated they felt more confident about their tech job prospects after attending a bootcamp. Get matched to a bootcamp today.

Find Your Bootcamp Match

The average bootcamp grad spent less than six months in career transition, from starting a bootcamp to finding their first job.

Start your career switch today

We use indexing to select and change the first item in our list, 99.95. This value has the index position zero. This is because lists are indexed starting from zero:

We can change our list by adding five to the current value of prices[0]:

prices[0] corresponds with the first item in our list (the one at index position ).

Our code returns a list with the same values as our first example:

Python Replace Item in List: Using a List Comprehension

A Python list comprehension may be the most Pythonic way of finding and replacing an item in a list. This method is useful if you want to create a new list based on the values of an existing one.

Using a list comprehension lets you iterate through items in an existing list and create a new list based on a certain criterion. You can generate a new list that only contains items beginning with “C” from an existing list, for instance.

Find Your Bootcamp Match

Select your interest
First name

Last name

Email

Phone number

By continuing you agree to our Terms of Service and Privacy Policy, and you consent to receive offers and opportunities from Career Karma by telephone, text message, and email.

Next, we define a list comprehension to replace the items in our list:

Our code returns our list of new prices:

A 10% discount has been successfully applied to every item.

Python Replace Item in List: Using a For Loop

You can replace items in a list using a Python for loop. To do so, we need to the Python enumerate() function. This function returns two lists: the index numbers in a list and the values in a list. We iterate over these two lists with a single for loop.

In this example, we’re going to use the same list of prices in our code:

We then define a for loop that iterates over this list with the enumerate() function:

The value “index” stores the index position of an item. “Item” is the value that correlates with that index position. The comma separates the two list values returned by the enumerate() method.

Retrieving two or more values from a method or another value is called unpacking. We have “unpacked” two lists from the enumerate() method.

«Career Karma entered my life when I needed it most and quickly helped me match with a bootcamp. Two months after graduating, I found my dream job that aligned with my values and goals in life!»

Venus, Software Engineer at Rockbot

Find Your Bootcamp Match

Our code successfully changes the items in our “prices” list based on our discount.

Conclusion

You can replace items in a Python list using list indexing, a list comprehension, or a for loop.

If you want to replace one value in a list, the indexing syntax is most appropriate. To replace multiple items in a list that meet a criterion, using a list comprehension is a good solution. While for loops are functional, they are less Pythonic than list comprehensions.

Are you interested in more resources to help you learn Python? If so, you should check out our How to Learn Python guide. This guide contains a list of top courses, books, and learning resources that will help you master the language.

Python list replace: How to replace string, integer in List

String in Python is an immutable Data type. Replacing a string with another string is a regular operation in any development. The string replace() method in Python will help us replace a string with a particular string in the list of Strings.

Python list replace

To replace an element in the Python list, use the list comprehension. To replace a string in a Python list, use the combination of list comprehension + string replace().

Example

Let’s see the following code example.

Output

We defined a Python list and then used the list comprehension to replace 4 with 5, return the new list, and then printed the list.

Python String replace() method replaces a specified phrase with another.

Let’s see another example in which we replace the Golang string to Go.

Output

If nothing particular is specified, then all occurrences of the specified phrase will be replaced.

List replace Using map() + lambda + replace()

Use the combination of Python map(), lambda function, and string replace() functions to replace a string with another string in the Python list.

See the following code.

Output

In the above code, we have defined the list and then used the map() function to replace PHP string to .Net String and convert that iterator into a list using the list() function.

Replace integer in Python List

To replace an integer with an integer in a Python list, use the ternary operator and list comprehension.

See the following code.

Output

In the above example, we have defined a list, and we need to replace 23 integer with 21 integer.

If it finds multiple integers, it will replace all the numbers with specified values. So keep in mind that. To do that using list comprehension, we have to use a ternary operator in the list.

So we have written if you find 23 on the list, then replace it with 21 and return the list.

That is it for this tutorial, and thanks for taking it.

4 Ways To Replace Items In Python Lists

Learn how to replace items in a Python list by solving basic algorithms a get ready for your next coding interview

Hope you’ll find them useful too! Now enjoy the article 😀

3 Data Engineering Courses To Advance Your Career In 2021

Join the data industry, change role or simply learn cutting-edge technologies by enrolling in Data Engineering…

Introduction

While preparing for your next Python coding round, you might have noticed that algorithms requiring to manipulate one or more lists appear rather frequently. Sooner or later, you should expect to encounter one of them during your interviews as well.

Algorithms requiring to manipulate one or more lists appear rather frequently. Sooner or later, you should expect to encounter one of them during your interviews as well.

In order to help you in the process of mastering this data structure and improve your coding skills, below I present 4 methods to replace an item in Python lists as well as four simple algorithms for you to test your skills.

Most of the classic interview questions can be solved with multiple approaches, so for each problem, try to come up with your solution first, before looking at the one I provided. Similarly to other skills, algorithmic interview is one area where you can greatly improve with consistent practice.

1. Indexing

The most straightforward way to replace an item in a list is to use indexing, as it allows you to select an item or range of items in an list and then change the value at a specific position, using the assignment operator:

For example let’s suppose you were working with the following list including six integers:

and you were asked to add 10 to the third integer from the left. Since lists are indexed starting from zero, you could use one of the following syntaxes to change the element with index = 2 that in our case in the number 12 :

Now try to practice this first method solving the following problem:

PROBLEM #1

In the result, the digits has to be stored such that the first digit of the number obtained by the sum, is at the head of the list, and each element in the list contains a single digit. You may assume the integer does not contain any leading zero, except the number 0 itself.

Note that our input list is made up of four non-negative integers that together represent the integer 9999. This in an edge case, because by adding 1 to this number, you will obtain an integer with 5 digits ( instead of the original 4) and a leading 1.

To account for these type of situations, the solution takes advantage of two conditional statements that start evaluating the digits from last to first ( using reverse() to flip the order of the indexes). If not equal to 9, ONLY the last digit is incremented by 1 through the now familiar syntax digits += 1 and the amended list is immediately returned, without evaluating the remaining indexes.

Alternatively, if the last digit is a 9, it is replaced by a 0 and the following ( second-to-last) digit is evaluated. If this is not equal to 9, then 1 is added and the amended list returned. Otherwise, if each one of following digits is a 9, then the function will return an list with a leading 1 and as many 0s as the number of the elements in the original list.