Get every Nth element in a List in Python

This tutorial will discuss about unique ways to get every nth element in a list in Python.

Table Of Contents

Method 1: Using Slicing

We can slice some elements from a list using the slicing operator i.e.

list[start, end , N]

It will select every Nth element from list from start to end index positions in list. Default value of start is 0, and the default value of end is the end of list. So, to get a sublist containing every Nth element from list, use the default values of start, and end. Also, provide the step size N in slicing operator i.e.

# Select every Nth element from List
subList = listOfNumbers[ : : N]

It should return a sublist containing every Nth element from list.

Let’s see the complete example,

listOfNumbers = [12, 42, 44, 68, 91, 72, 71, 81, 82, 91, 92, 93]

N = 3

# Select every Nth element from List
subList = listOfNumbers[ : : N]

print(subList)

Output

[12, 68, 71, 91]

Method 2: Using itertools.islice()

The itertools provides a method islice(). It accepts the following arguments,

• An iterable sequence, from which we need to slice the elements.
• The start position in the sequence, from which it will start the slicing. Default value is 0.
• The end position in the sequence, at which it will stop the slicing. Default value is None i.e. end of list.
• Step size N: It specifies the number of values that need to be skipped between successive calls.

It selects every Nth element in the range, and returns an iterator pointing to the selected elements. We can use it to select every Nth element from a complete list.

Let’s see the complete example,

import itertools

listOfNumbers = [12, 42, 44, 68, 91, 72, 71, 81, 82, 91, 92, 93]

N= 3

# Select every Nth element from List
subList = list(itertools.islice(listOfNumbers, 0, None, N))

print (subList)

Output

[12, 68, 71, 91]

Summary

We learned about different ways to get every Nth element from a List in Python. Thanks.