How to add element to list python

How to add Elements to a List in Python

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In this tutorial, we will learn different ways to add elements to a List in Python.

Methods to add elements to List in Python

There are four methods to add elements to a List in Python.

Python add elements to List Examples

We can add an element to the end of the list or at any given index. There are ways to add elements from an iterable to the list. We can also use + operator to concatenate multiple lists to create a new list.

1. append()

This function add the element to the end of the list.

2. insert()

This function adds an element at the given index of the list. It’s useful to add an element at the specified index of the list.

3. extend()

This function append iterable elements to the list. It is useful to append elements from an iterable to the end of the list.

4. List Concatenation

If you have to concatenate multiple lists, you can use the “+” operator. This will create a new list and the original lists will remain unchanged.

The new list will contain elements from the list from left to right. It’s similar to the string concatenation in Python.

Conclusion

It’s very easy to add elements to a List in Python programming. We can append an element at the end of the list, insert an element at the given index. We can also add a list to another list. If you want to concatenate multiple lists, then use the overloaded + operator. References:

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Append Items

To add an item to the end of the list, use the append() method:

Example

Using the append() method to append an item:

Insert Items

To insert a list item at a specified index, use the insert() method.

The insert() method inserts an item at the specified index:

Example

Insert an item as the second position:

Note: As a result of the examples above, the lists will now contain 4 items.

Extend List

To append elements from another list to the current list, use the extend() method.

Example

Add the elements of tropical to thislist :

The elements will be added to the end of the list.

Add Any Iterable

The extend() method does not have to append lists, you can add any iterable object (tuples, sets, dictionaries etc.).

Example

Add elements of a tuple to a list:

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Python Add to List: The Complete Guide

Python add to List

To add elements to a list in Python, use the list.append() method. The list.append() method is a built-in method that appends an element to the end of the list. There are other ways to add elements to the Python list,

Lists work similarly to strings and use the len() function and square brackets [ ] to access data, with the first element at index 0.

List append()

Python list append() method takes an argument as a single element and adds it at the end of a list.

The length of a list increases by one.

Syntax

The method takes a single argument.

Parameters

element: An element to be added at the end of the List

The element can be numbers, strings, dictionaries, another list, and so on.

The method doesn’t return any value (returns None).

See the following code example.

Output

How to add List into List

Let’s see how to add the List to the List in Python.

Output

From the output, you can see that a new list is added as an item to the mando list.

List extend()

Python list extend() method inserts the specified list items (or any iterable) to the end of the current List. The extend() extends the List by adding all elements of the List (passed as an argument) to an end.

Unlike Python append(), it adds items individually.

Syntax

Parameters

The extend() function takes only one parameter, which is iterable like List, tuple, dict, or set.

See the following code example.

Output

From the output, you can see that the extend() method did not append the whole List; instead, it adds an individual item of that list at the end of the List.

Time Complexity:

Append has constant time complexity, i.e., O(1).
Extend has the time complexity of O(k), where k is the length of the List, which needs to be added.

List insert()

Python list insert() is a built-in Python function that adds an element to the given index of the List. To add an element to the specified index of the List, then the insert() method of Python is handy.

See the following code.

Output

In the above example, first, we have defined a list and then use the input() function to get the user input.

We have to get two inputs from the user because the insert() function takes two parameters.

After getting the inputs, we update the List using the insert() function and print the List.

List Concatenation

If you have to concatenate multiple lists, then you can use the “+” operator. This operation will create the new List, and the original List will remain unchanged.

So, this way is a kind of Pure function in functional programming.

See the following code.

Output

The + operator just concatenates the two lists and makes one List.

Table of Contents

In this tutorial, you’ll learn how to:

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In the highlighted line, you perform two operations at the same time:

.append() Adds a Single Item

.append() Returns None

Populating a List From Scratch

A common problem that you might face when working with lists in Python is how to populate them with several items for further processing. There are two ways to do this:

In the next few sections, you’ll learn how and when to use these techniques to create and populate Python lists from scratch.

This way of populating lists is fairly common in Python. However, the language provides some convenient constructs that can make the process a lot more efficient and Pythonic. One of these constructs is a list comprehension, which you’ll see in action in the next section.

Using a List Comprehension

Note: Python also offers other kinds of comprehensions, such as set comprehensions, dictionary comprehensions, and generator expressions.

Suppose you need square_root() to provide your users with detailed information about the progress of calculating the square root of the input list of numbers. To report the operation progress, you can use print() :

Implementing a Stack

A stack is a data structure that stores items on top of each other. Items come in and out of the stack in a Last-In/First-Out (LIFO) fashion. Typically, a stack implements two main operations:

Note: In Python, using exceptions to control the flow of a program is a common pattern. Python developers favor this coding style, known as EAFP (Easier to Ask for Forgiveness than Permission), over the coding style known as LBYL (Look Before You Leap). To learn more about these two coding styles, check out LBYL vs EAFP: Preventing or Handling Errors in Python.

EAFP can help you prevent race conditions, improve the general performance of a program or a code fragment, and prevent errors from passing silently.

Here are some examples of how you can use Stack in practice:

That’s it! You’ve coded a stack data structure that implements the push and pop operations. It also provides functionality to get the length of the underlying list and to print the entire stack in a user-friendly manner.

Implementing a Queue

Queues are data structures that commonly manage their items in a First-In/First-Out (FIFO) fashion. Queues work like a pipe in which you push in new items at one end, and old items pop out from the other end.

Adding an item to the end of a queue is known as an enqueue operation, and removing an item from the front, or beginning, of a queue is known as a dequeue operation.

You’ll learn more about using deques a little later in the tutorial.

array.append()

Python’s array.array() provides a sequence-like data structure that can compactly represent an array of values. These values must be of the same data type, which is limited to C-style data types, such as characters, integer numbers, and floating-point numbers.

array.array() takes the following two arguments:

The documentation of array provides complete information about all the allowed type codes that you can use when creating arrays. The following example uses the «i» type code to create an array of integer numbers:

To create an array, you need to provide a single-character code to define the data type of the values in the array. You can also provide an optional list of values with the appropriate type to initialize the array.

In contrast, if you have an array with floating-point numbers and try to add integer numbers to it, then your operation will succeed:

deque.append() and deque.appendleft()

Note: The name deque is pronounced “deck” and stands for double-ended queue.

collections.deque() takes the following two optional arguments:

Conclusion

In this tutorial, you learned:

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Related Tutorial Categories: basics python

How to Add Elements to a List in Python?

In Python, there are always multiple ways to accomplish the same thing—but with subtle differences in the side effects. A great coder will always choose the most effective way for the problem at hand.

This tutorial shows you six different ways to add elements to a list in Python. In a nutshell, the different ways to add one or more elements to a list are:

Try It Yourself: Before we dive into each of those methods, let’s try them yourself in our interactive Python shell!

Exercise: Use each method to add yet another integer element 42 to each list. Which method is the best one to add multiple elements?

Next, you’ll learn about each method in a video tutorial and short example code snippet. I’ve written in-depth articles for each method so feel free to follow the references given in each method.

Table of Contents

Method 1: append()

Method 2: extend()

Method 3: insert()

Method 4: Slice Assignment

Method 5: List Concatenation with +

If you use the + operator on two integers, you’ll get the sum of those integers. But if you use the + operator on two lists, you’ll get a new list that is the concatenation of those lists.

Method 6: List Concatenation with Unpacking *

There are many applications of the asterisk operator. But one nice trick is to use it as an unpacking operator that “unpacks” the contents of a container data structure such as a list or a dictionary into another one.

A great advantage is that you can quickly unpack all elements of two or more list into a new list.

Python List Methods Cheat Sheet

Here’s your free PDF cheat sheet showing you all Python list methods on one simple page. Click the image to download the high-resolution PDF file, print it, and post it to your office wall:

Discussion

Let’s summarize the strengths and weaknesses of the different methods:

Where to Go From Here?

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