Remove duplicates from a list in-place

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How can one make a list contain only unique items while preserving order AND updating it in-place?

I know that a set can be used, but it will not guarantee ordering.


Use a supporting set, and a while loop:

def unique(arr):
    tmp_set = set()
    i = 0
    while i < len(arr):
        if arr[i] in tmp_set:
            del arr[i]
        else:
            tmp_set.add(arr[i])
            i += 1

The above will update the array in-place, and preserve ordering of the elements as well.

Python - Ways to remove duplicates from list, Recommended Posts: Remove duplicates from an array of small primes � Search an element in a sorted and rotated array with duplicates � Remove duplicates� Remove any duplicates from a List: mylist = ["a", "b", "a", "c", "c"] mylist = list (dict.fromkeys (mylist)) print(mylist) Try it Yourself ».


Enhanced CodeSpeed solution.

lst = [1, 2, 2, 1, 1]

seen = set()

length = len(lst) - 1

i = 0
while i < length:
    if lst[i] in seen:
        del lst[i]
        i -= 1
    seen.add(lst[i])
    i += 1
    length = len(lst)

print(lst)

Remove duplicates from sorted array, We need to take a list, with duplicate elements in it and generate another list which only contains the element without the duplicates in them. Examples: Input : [2, 4,� Given a sorted array nums, remove the duplicates in-place such that each element appear only once and return the new length. Do not allocate extra space for another array, you must do this by modifying the input array in-place with O (1) extra memory. Example 1:


You can use a loop to iter over the entries in the list one by one and insert them into a newlist only if they are not present in the new list.

lst = [3,3,3,1,2,2,4]

my_list = []

for i in lst:
    if i not in my_list:
        my_list.append(i)
my_list

# Output - [3, 1, 2, 4]

I hope this helps.

Python Remove Duplicates from a List, The common approach to get a unique collection of items is to use a set . Sets are unordered collections of distinct objects. To create a set from any iterable, you� DeDupe List Remove duplicate lines from a list Paste lines into the field, select any options below, and press Submit. Results appear at the bottom of the page.


Removing duplicates in lists, Learn how to remove duplicates from a List in Python. Example. Remove any duplicates from a List: mylist = ["a", "b"� Given a sorted array, the task is to remove the duplicate elements from the array. Examples: // C++ program to remove duplicates in-place . #include<iostream>


How to remove duplicates from a Python List, Dictionaries in Python cannot include duplicate keys, and so if we convert our list to a dictionary, it will automatically remove any duplicate values. Method to handle dropping duplicates: ‘first’ : Drop duplicates except for the first occurrence. ‘last’ : Drop duplicates except for the last occurrence. False: Drop all duplicates. inplace bool, default False. If True, performs operation inplace and returns None. Returns Series. Series with duplicates dropped.


How to Remove Duplicates from a List in Python, In this article, we'll look at how we can remove duplicate elements from List in Python. There are multiple ways of approaching this problem, and we will show.