Get unique values from a List in Python

In this article, we will discuss different ways to fetch unique values from a list in Python.

Table Of Contents

Introduction

Suppose we have a list of numbers i.e.

[12, 48, 23, 48, 54, 12, 71, 48, 71, 48, 23, 48]

This list has certain repeated elements. But we want to find out all unique value in this list. Like,

[12, 48, 23, 54, 71]

There are different ways to get unique values from a list. Let’s discuss them one by one,

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Get unique values in list using for loop

Create a new empty list X. Then iterate over all elements in the given list and for each element check if it exists in the new list X or not. If not then add that element to list X. When for loop ends, the list X will have all unique values from the given list.

For example,

listOfNums = [12, 48, 23, 48, 54, 12, 71, 48, 71, 48, 23, 48]

uniqueElements = []

for elem in listOfNums:
    if elem not in uniqueElements:
        uniqueElements.append(elem)

print(uniqueElements)

Output:

[12, 48, 23, 54, 71]

We fetched all unique values from a list in Python.

Get unique values in list using set

A set in python can have unique values only. So, to find the unique values from a list, we can create a set from the list. This set will have unique values only. Then we can cast this set to a new list.

For example,

listOfNums = [12, 48, 23, 48, 54, 12, 71, 48, 71, 48, 23, 48]

# Get unique values from a list
uniqueElements = list(set(listOfNums))

print(uniqueElements)

Output:

[71, 12, 48, 54, 23]

Get unique values in list using NumPy

Convert list to a numpy array and then pass that to numpy.unique() function. It will return an array of unique values only. Then cast it back to a list. This list will have unique values only.

For example,

import numpy as np

listOfNums = [12, 48, 23, 48, 54, 12, 71, 48, 71, 48, 23, 48]

# Get unique values from a list
uniqueElements = list(np.unique(np.array(listOfNums)))

print(uniqueElements)

Output:

[12, 23, 48, 54, 71]

Get unique values in list using Counter

Create a Counter object from the list. This counter object, will have a mapping of unique values from list and thier occurrence count. We can cast this counter object to a list. This list will have unique values only from the original list.

For example,

from collections import Counter

listOfNums = [12, 48, 23, 48, 54, 12, 71, 48, 71, 48, 23, 48]

# Get unique values from a list
uniqueElements = list(Counter(listOfNums))

print(uniqueElements)

Output:

[12, 23, 48, 54, 71]

Summary

We learned about different ways to get unique elements from a list in Python. Happy Coding.

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Thanks for reading.

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