How to Create a Python List?

Definition Lists: A Python list is an ordered sequence of arbitrary Python objects. It is a mutable object by itself so, unlike Python sets, you can modify a Python list.

In this article, you’ll learn everything you need to know on how to create Python lists.

Overview — Creating a List in Python

There are many ways of creating a list in Python. Let’s get a quick overview in the following table:

CodeDescription
[]Square bracket: Initializes an empty list with zero elements. You can add elements later.
[x1, x2, x3, … ]List display: Initializes an empty list with elements x1, x2, x3, … For example, [1, 2, 3] creates a list with three integers 1, 2, and 3.
[expr1, expr2, ... ]List display with expressions: Initializes a list with the result of the expressions expr1, expr2, … For example, [1+1, 2-1] creates the list [2, 1].
[expr for var in iter]List comprehension: applies the expression expr to each element in an iterable.
list(iterable)List constructor that takes an iterable as input and returns a new list.
[x1, x2, ...] * nList multiplication creates a list of n concatenations of the list object. For example [1, 2] * 2 == [1, 2, 1, 2].

You can play with some examples in our interactive Python shell:

Exercise: Use list comprehension to create a list of square numbers.

Let’s dive into some more specific ways to create various forms of lists in Python.

BELOW I’LL GIVE YOU A PDF CHEAT SHEET OF THE MOST IMPORTANT PYTHON LIST METHODS. So keep reading!

Python Create List of Size

Problem: Given an integer n. How to initialize a list with n placeholder elements?

# n=0 --> []
# n=1 --> [None]
# n=5 --> [None, None, None, None, None]

Solution: Use the list concatenation operation *.

n = 5
lst = [None] * n
print(lst)
# [None, None, None, None, None]

You can modify the element n as you like. For a detailed discussion on this topic, please visit my blog tutorial on How to Create a List with a Specific Size n? The tutorial also contains many visualizations to teach you the ins and outs of this method (and gives you some powerful alternatives).

Python Create List of Strings

You can use the previous method to create a list of n strings:

n = 3
lst = ['xyz'] * n
print(lst)
# ['xyz', 'xyz', 'xyz']

But do you want to create a list of numbers?

Python Create List of Numbers

Simply replace the default strings with the default numbers:

n = 3
lst = [1] * n
print(lst)
# [1, 1, 1]

A special case is the number:

Python Create List of Zeros

This creates a list of zeros:

n = 3
lst = [0] * n
print(lst)
# [0, 0, 0]

But what if you want to create a list of consecutive numbers 0, 1, 2, …?

Python Create List from Range

To create a list of consecutive numbers from x to y, use the range(x, y) built-in Python function. This only returns a range object which is an iterable. But you can convert the iterable to a list using the list(...) constructor:

print(list(range(2, 4)))
# [2, 3]

print(list(range(2, 6)))
# [2, 3, 4, 5]

print(list(range(2, 10, 2)))
# [2, 4, 6, 8]

You can see that the second argument (the stop index) is not included in the range sequence. The third argument of the range(start, stop, step) function is the optional step size that allows you to skip step numbers of the series of continuous numbers.

Python Create List from 0 to 100

A special situation arises if you want to create a list from 0 to 100 (included). In this case, you simply use the list(range(0, 101)) function call. As stop argument, you use the number 101 because it’s excluded from the final series.

print(list(range(0, 101)))
# [0, 1, ..., 100]

print(list(range(101)))
# [0, 1, ..., 100]

It’s actually not necessary to give the default start index 0, so you can just skip it.

Python Create List with For Loop

To create a list with a for loop, you first initialize the empty list, and then subsequently append an element to the list:

lst = []
for x in range(10):
    # Append any initial element here:
    lst.append(x)

print(lst)
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

You can learn more about the single-line for loop in this article.

Python Create List of Lists

However, there’s a small problem if you want to create a list with mutable objects (such as a list of lists):

lst = [[]] * n
print(lst)
# [[], [], [], [], []]

lst[2].append(42)

print(lst)
# [[42], [42], [42], [42], [42]]

Changing one list element changes all list elements because all list elements refer to the same list object in memory:

The solution is to use list comprehension (see my detailed blog tutorial on list comprehension for a complete guide):

lst = [[] for _ in range(n)]
print(lst)
# [[], [], [], [], []]

lst[2].append(42)
print(lst)
# [[], [], [42], [], []]

In the following visualization, you can see how each element now refers to an independent list object in memory:

Exercise: Run the visualization and convince yourself that only one element is modified! Why is this the case?

Python Create List of Tuples

A similar approach can be used to create a list of tuples instead of a list of lists.

n = 5
lst = [() for _ in range(n)]
print(lst)

lst[2] = (1, 2, 3)
print(lst)

'''
[(), (), (), (), ()]
[(), (), (1, 2, 3), (), ()]
'''

You first initialize the list with empty tuples. Tuples are immutable so you cannot change them. But you can overwrite each list element with a new tuple like you did in the example with the third element and tuple (1, 2, 3).

Python Create Equally Spaced List

To create an equally spaced list, use the np.linspace() function of the NumPy library. Here’s a short tutorial on the matter: