How To Create An Empty List In Python?

In this tutorial, I will explain how to create an empty list in Python. As a Python developer working on a project for one of my clients, I recently encountered a situation where I needed to initialize an empty list to store data. Let us explore different ways to create an empty list.

Table of Contents

Empty List in Python

An empty list in Python is a list that contains no elements. It is represented by a pair of square brackets [] with nothing in between. Empty lists are commonly used as a starting point to build a list incrementally or to store data that will be added later in the program.

For example, let’s say you’re developing a web application for a company based in New York, and you need to store the names of employees. You can start by creating an empty list like this:

employees = []

Read How to Remove All Instances of an Element from a List in Python?

Create an Empty List in Python

To create an empty list in Python, you can use square brackets [] or the list() constructor. For example:

empty_list1 = []
empty_list2 = list()

Both empty_list1 and empty_list2 are empty lists that you can now populate with data as needed in your Python program.

1. Use Square Brackets []

The simplest way to create an empty list is by using a pair of square brackets [] in Python. This is also known as the “literal” method. Here’s an example:

empty_list = []
print(empty_list)

Output:

[]

You can refer to the screenshot below to see the output.

This is the simplest way to create an empty list in Python.

Check out How to Remove an Element from a List by Index in Python?

2. Use the list() Constructor

Another way to create an empty Python list is by using the list() constructor. The list() function creates a new empty list when called without any arguments. Here’s an example:

empty_list = list()
print(empty_list)

Output:

[]

You can refer to the screenshot below to see the output.

You can create an empty list using an empty pair of square brackets [] or the type constructor list().

Read How to Add an Element to the Beginning of a List in Python?

Use Cases for Empty Lists

Empty lists have various use cases in Python programming. Let’s explore a few scenarios where empty lists come in handy.

1. Build Lists Incrementally

One common use case for empty lists is to build lists incrementally. You start with an empty list and then append elements to it as needed. This approach is useful when you don’t know the number of elements in advance or when you want to populate the list based on certain conditions.

For example, let’s say you’re creating a program to manage customer orders for a restaurant in Chicago. You can start with an empty list called orders and append each order as it comes in:

orders = []

while True:
    order = input("Enter an order (or 'done' to finish): ")
    if order == 'done':
        break
    orders.append(order)

print("Orders:", orders)

Output:

Enter an order (or 'done' to finish):

You can refer to the screenshot below to see the output.

Check out How to Count the Frequency of Elements in a Python List?

2. Store Results from Computations

Empty lists are also useful for storing results from computations or data processing tasks. You can initialize an empty list and then populate it with the results as you iterate over a dataset or perform calculations.

For instance, suppose you’re analyzing sales data for a retail store in Los Angeles. You want to calculate the total revenue for each month and store the results in a list. You can start with an empty list called monthly_revenue and append the calculated revenue for each month:

sales_data = [1000, 1500, 1200, 1800, 2000, 1700]  # Example sales data
monthly_revenue = []

for sales in sales_data:
    revenue = sales * 0.1  # Assuming a 10% profit margin
    monthly_revenue.append(revenue)

print("Monthly Revenue:", monthly_revenue)

Check out How to Initialize a List of Size N in Python?

3. Initialize Lists with a Specific Size

Sometimes you may need to initialize a list with a specific size, where each element is an empty list itself. This is commonly used when working with multi-dimensional lists or matrices.

For example, let’s say you’re creating a program to track student grades for a school in Houston. You want to initialize a 2D list to store the grades for each student in different subjects. You can use a list comprehension to create a list of empty lists:

num_students = 5
num_subjects = 3

grades = [[] for _ in range(num_students)]

In this example, grades is a list of 5 empty lists, representing 5 students. Each empty list will store the grades for the respective student in different subjects.

One of the most convenient features of Python is the ability to create empty lists which can be used to store data objects.

Read How to Convert a List to a Pandas DataFrame in Python?

Conclusion

In this tutorial, I explored how to create an empty list in Python using square brackets [] and the list() constructor. We also discussed various use cases for empty lists, such as building lists incrementally, storing results from computations, and initializing lists with a specific size.