To initialize a list of size N in Python, the easiest way is to use * to multiply a single item list by N. 

n = 100

list_of_size_n = [0] * n
list_of_size_n = [None] * n

When working with numbers in a Python program, it’s possible you want to initialize an array of size N in Python.

Arrays in Python are called lists, and we can easily create a list of size N in our Python code.

To initialize a list of size N in Python, the easiest way is to use * to multiply a single item list by N.

Depending on what you are going to do with this list, whether it is going to be filled later in your program or used as placeholders, you can fill it with 0’s or None’s.

Below shows you how to create a list of size N in Python.

n = 100

list_of_size_n = [0] * n
list_of_size_n = [None] * n

How to Create List from 1 to N in Python

When working with numbers in a Python program, it’s possible you want to create an array from 1 to n in Python.

We can easily create a list of the numbers 1 to n in our Python code.

The range() function takes in 3 arguments. The first is the starting point, the second is the ending point, and the third argument is the step size.

For example, if I want all the numbers between 1 and 10, I’d call the range function in the following way.

numbers_1_to_10 = list(range(1,11))

We can define a function which will create a list from 1 to N. This will also give you a list of size N.

Below is an example of a function in Python which returns a list with numbers from 1 to N.

def listFrom1toN(n):
    return list(range(1,n+1))

print(listFrom1toN(13))

#Output:
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]

Hopefully this article has been useful for you to learn how to initialize an array of size N in Python.

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Last Update: March 12, 2024