Append in Python: What Is It, What Does It Do, and How to Use It?

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Published on August 18th, 2022

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Regarding real-world Python applications, developers may need to add a single item to an existing data structure multiple times. For example, to add an object to an already existing collection type. That is why the append method in Python exhibits its value.

Append in Python is a predefined method for adding a single item to certain types of collections. In the absence of the append method, developers would have to change the code of the entire group to add a single value or item. Its primary use case is seen for the list collection type.

Table of Contents

Introduction

Fundamental data types in Python permit us to store a single value under a symbolic name. This roughly corresponds to the mathematical notation of variables. In a way, the value is given a name, so you don’t have to remember the actual value or its address in computer memory, just a simple, descriptive name.

But basic data types won’t do the job if you need to store a collection of values under a single variable name. You will be required to use more complex data structures. Python has four data types for storing an array of values under the same name – Tuple, Set, Dictionary, and List. We will focus on the list in this blog.

List collection type and its role in joining.

Python offers several collection types for storing multiple objects and values in a single reference variable. A list is one such type of collection. Unlike arrays, the best thing about lists is that you can store values of different data types. So you can easily keep an integer, character, or float in a single list.

List values are indexed from 0, and the last number is n-1, where n is the total values in the list. Because each value has a specific index number, you can add the same value to the list multiple times. Accepting the same values and different data types makes lists one of the best collections to use in Python. Here’s how to create a list:

“`

list_name = [1, “hello”, 2.0 , “world”]

“`

From the syntax above, you need to separate each value in the list with a comma. You can use the index number to check the total length of the list using the predefined len() function and any specific value.

Our Learners Also Read: Advantages and Disadvantages of Python

How to add elements to a Python list using append()

Adding elements to a list is equivalent to adding those elements to the end of an existing list. Python provides several ways to do this, but the method tailored specifically for this task is append(). It has a reasonably straightforward syntax:

example_list.append(element)

This code snippet adds an element to the end of example_list (which is of type list). As we mentioned earlier, a list can contain elements of different data types. The elements can therefore be of any data type int, float, str, list, tuple, etc.

In the following sections, we’ll walk through some practical examples illustrating how to add an individual element to a list and how to add one list to another.

Note: In these examples, we utilize a list containing elements of different types.

How to add one element to the end of a Python list

Adding a single element illustrates Python’s primary purpose of the append() method. Suppose you have a list of examples:

“`

example_list = [1, 3.14, ‘abcd’]

“`

You could add 5 to the end of exampe_list as follows:

“`example_lsit.append(5)“`

Now example_list will have 5 appended to its end:

[1, 3.14, ‘abcd’, 5]

How to concatenate one list to another in Python

Suppose you have two lists and want to join one to the other:

example_list = [1, 3.14, ‘abcd’]

secondary_list = [4, 3, 2, 1]

The append() method does not deliver a way to join two lists together in a single method call. If you try to append these two lists using append(), the entire secondary_list will be added as a single example_list element, creating a nested list:

example_list.append(secondary_list)

print (list of examples)

Now example_list contains the following elements, which are probably not what you originally wanted:

[1, 3,14, ‘abcd’, [4, 3, 2, 1]]

Appending one list to another using append() is achieved by iterating through all the elements of the list we want to append and appending each one to the original list:

for element in secondary_list:

example_list.append(element)

print (list of examples)

This way, we added a secondary_list to the end of the example_list:

[1, 3,14, ‘abcd’, 4, 3, 2, 1]

Alternatives to append() in Python

Python List has several other methods for adding elements and append(). The most notable are extend() and insert(). We will understand their differences and the append() method in the following subsections.

append() vs extend()

As we’ve seen in the last sections, append() is designed to add one element to the end of a list. While, extend() is used to add more elements to the end of a list – effectively appending one list to another. Let’s see how extend() works:

example_list = [1, 3.14, ‘abcd’]

secondary_list = [4, 3, 2, 1]

example_list.extend(secondary_list)

print (list of examples)

Exit:

[1, 3,14, ‘abcd’, 4, 3, 2, 1]

Notice how extend() concatenates two lists in one call, and append() needs to be called once for each element of the list you want to add! It’s a convenient method to recognize as an alternative.

append() vs insert()

There is no other way to insert an element at a specific location in the list using append(). It will automatically add it to the bottom of the list. This is where insert() comes in!

Unlike append() and extend(), it takes two arguments – one is the element you want to insert, and the other is the index of that element in the list.

Let’s take an example, if you want to add ‘asdf’ to the end of example_list, you use example_lsit.append(‘asdf’) as we saw in the previous sections. But if you want to add it in a specific place, say between 3.14 and ‘abcd’, you have to use insert():

example_list = [1, 3.14, ‘abcd’]

# Insert `asdf` element at index `2`

example_list.insert(2, ‘asdf’)

print (list of examples)

The result is:

[1, 3.14, ‘asdf’, ‘abcd’]

Note the difference in the indexing of the original and the resulting list. In the original example_list, the element at index 2 is ‘abcd’. After adding ‘asdf’ is at index 2, and ‘abcd’ is moved to index 3.

Conclusion

Append in Python is essential for adding a single item to the end of a list, array, deque, or other collections and data structures on the go. Python has already become and continues to become one of the most popular programming languages in the world. To pursue a career in software development, learning the basics like append in Python is essential.