How To Get Unique Values From a List in Python – Definitive Guide

Published on: | Last updated on: January 12, 2023

Python lists allow storing non-unique values.

You can get unique values from a list in Python using a set(num_list) statement.

Basic Example

num_list = [10, 20,30,30,40,50,50]

unique_numbers = list(set(num_list))

unique_numbers

In this tutorial, you’ll learn how to get unique values from a list in Python using different available methods.

Using Set() method

The set() method returns a new set with the unique objects available in the iterable(Example: List).

  • Use the set() method to get unique values from a list.

Code

num_list = [10, 20,30,30,40,50,50]

unique_numbers = set(num_list)

unique_numbers

Output

    {40, 10, 50, 20, 30}

If you want to have the unique items in the list object instead of set,

  • Convert the set object into the list again
num_list = [10, 20,30,30,40,50,50]

unique_numbers = list(set(num_list))

unique_numbers

Output

    [40, 10, 50, 20, 30]

Using numpy.unique

The unique() method returns the unique items from the array.

  • Convert a list to a NumPy array using np.array() method
  • Use the NumPy array with the np.unique() method to get the unique values

Code

import numpy as np

num_list = [10, 20,30,30,40,50,50]

x = np.array(num_list)

np.unique(x)

Output

You’ll see the below output. The unique items will be available in the array.

    array([10, 20, 30, 40, 50])

Using Append

The append() method appends new items to the existing list.

To get the unique values from the list using the append() method,

  • Iterate over the list
  • Check if the item is available in the new array
  • If the item is NOT existing, add it to the new array. Else, do not add it.

Code

def find_unique(num_list):

    unique_list = []

    for x in num_list:

        if x not in unique_list:
             unique_list.append(x)

    for x in unique_list:
        print(x)



num_list = [10, 20,30,30,40,50,50]

find_unique(num_list)

Output

    10
    20
    30
    40
    50

Using Counter

The counter is a dict subclass for counting hashable objects.

You can also use the counter class from the python collection to get the unique values from a list.

  • It counts the object and has the count of each item as a dictionary.
  • The dictionary key consists of the items in the list, and the values denote the number of times the item occurs.

To get the unique values, you can print the counter dictionary using the star * operator. The * operator displays only the keys from the dictionary. This means that only the unique values from the list are printed.

Code

from collections import Counter

num_list = [5, 10, 5, 10, 20, 30]

print(*Counter(num_list))

Output

    5 10 20 30

If you would like to know the number of occurrences of each object, directly use the counter object as demonstrated below.

Counter(num_list)

Output

    Counter({5: 2, 10: 2, 20: 1, 30: 1})

Additional Resources

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