How to Convert a List into Ordered Set in Python? Last Updated : 07 Jan, 2025 Comments Improve Suggest changes Like Article Like Report The task is to turn a list into an ordered set, meaning we want to remove any duplicate items but keep the order in which they first appear. In this article, we will look at different ways to do this in Python.Using OrderedDict.fromkeys()OrderedDict.fromkeys() method removes duplicates from a list and keeps the original order of the elements. It works by using an OrderedDict, which remembers the order of items as they are added.Example: Python from collections import OrderedDict # list a = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3] # Remove duplicates while preserving order res = list(OrderedDict.fromkeys(a)) # Print the result print(res) Output[3, 1, 4, 5, 9, 2, 6] Using dict.fromkeys()dict.fromkeys() method removes duplicates from a list while preserving the order of elements. Since dictionaries in Python 3.7+ maintain insertion order.Example: Python # list a = [1, 2, 3, 2, 1, 4, 5] # Remove duplicates while preserving order res = list(dict.fromkeys(a)) print(res) Output[1, 2, 3, 4, 5] Using for loop for loop iterate through the list, tracking seen elements with a set. It removes duplicates while preserving the order of the original list.Example: Python # list a = [1, 2, 3, 2, 1, 4, 5] # Initialize an empty list to store the result res = [] # Initialize set `s` to track seen elements s = set() # Iterate through `a` for i in a : # If the item is not already in `s` if i not in s: # Add the item to the `res` res.append(i) # Mark item as seen by adding it to `s` s.add(i) print(res) Output[1, 2, 3, 4, 5] Comment More infoAdvertise with us Next Article How to Convert a List into Ordered Set in Python? venkateshk1220 Follow Improve Article Tags : Python Python Programs python-list Python set-programs Practice Tags : pythonpython-list Similar Reads Convert set into a list in Python In Python, sets are unordered collections of unique elements. While they're great for membership tests and eliminating duplicates, sometimes you may need to convert a set into a list to perform operations like indexing, slicing, or sorting. 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