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Ways to remove duplicates from list in Python

Last Updated : 11 Jul, 2025

In this article, we'll learn several ways to remove duplicates from a list in Python. The simplest way to remove duplicates is by converting a list to a set.

We can use set() to remove duplicates from the list. However, this approach does not preserve the original order.

a = [1, 2, 2, 3, 4, 4, 5]

# Remove duplicates by converting to a set
a = list(set(a))

print(a)

Note: Using set() removes duplicates but does not guarantee the order of elements.

Let's explore other different ways to remove duplicates from list:

To remove duplicates while keeping the original order, we can use a loop (for loop) to add only unique items to a new list.

a = [1, 2, 2, 3, 4, 4, 5]

# Create an empty list to store unique values
res = []

# Iterate through each value in the list 'a'
for val in a:
  
    # Check if the value is not already in 'res'
    if val not in res:
      
        # If not present, append it to 'res'
        res.append(val)

print(res)

Note: This method preserves the original order but may be slower for large lists due to repeated membership checks ( ‘in’ operator).

List comprehension is another way to remove duplicates while preserving order. This method provides a cleaner and one-liner approach.

a = [1, 2, 2, 3, 4, 4, 5]

# Create an empty list to store unique values
res = []

# Use list comprehension to append values to 'res'
# if they are not already present
[res.append(val) for val in a if val not in res]

print(res)

Note: This method is concise but it is less efficient for large lists similar to the loop approach.

Dictionaries maintain the order of items and by using dict.fromkeys() we can create a dictionary with unique elements and then convert it back to a list.

a = [1, 2, 2, 3, 4, 4, 5]

# Remove duplicates using dictionary fromkeys()
a = list(dict.fromkeys(a))

print(a)

Note: This method is generally faster than the loop method for larger lists.

Python - Ways to remove duplicates from list

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