Find Index of Duplicate Elements in List in Python (2 Examples)
Hi! This short tutorial will show you how to get the index of duplicate elements in a list in the Python programming language.
Here is an overview:
Let’s get into the Python code!
Create Example List
So, in your Python coding IDE, run the code below to create the example list:
my_list = [1, 2, 3, 4, 2, 5, 6, 4] print(my_list) # [1, 2, 3, 4, 2, 5, 6, 4] print(type(my_list)) # <class 'list'>
Now that we have created the example list, we will consider two ways to return the index of the duplicate elements in the list.
Example 1: Get Index of Duplicate Elements in List Using for Loop & enumerate() Function
indexes =  for i, v in enumerate(my_list): if my_list.count(v) > 1 and i not in indexes: indexes.append(i) print(indexes) # [1, 3, 4, 7] print(type(indexes)) # <class 'list'>
Here, we use a for loop along with the
enumerate() function to iterate through the elements of the list along with their corresponding indices.
We first initialize an empty list called
indexes to store the indices of the duplicate elements.
Inside the loop, we check if the current element occurs more than once in the list by using the count() method.
If it does and the current index is not already in
indexes, we append the index to
Finally, we use the print() function to print
indexes, which contains the indices of the duplicate elements in the given list.
Example 2: Get Index of Duplicate Elements in List Using collections Module
In this next example, we will use Python’s built-in collections module to obtain the index of the duplicate elements in the list:
from collections import Counter counts = Counter(my_list) indexes = [index for index, value in enumerate(my_list) if counts[value] > 1] print(indexes) # [1, 3, 4, 7] print(type(indexes)) # <class 'list'>
In this example, we first import the Counter class from the collections module.
Next, we create an instance of the Counter class called
counts by passing
my_list as an argument. The Counter class provides a convenient way to count the occurrences of elements in a collection.
We then use a list comprehension to iterate through
my_list using the
enumerate() function and checking if the count of the current value in
my_list (obtained from
counts[value]) is greater than 1.
If it is, the index is appended to
Finally, we print the
indexes list, which contains the indices of the duplicate elements in the given list.
Video, Further Resources & Summary
Do you need more explanations on how to find the index of duplicate elements in a list in Python? Then you should have a look at the following YouTube video of the Statistics Globe YouTube channel.
In the video, we explain in some more detail how to find the index of duplicate elements in a list in Python.
The YouTube video will be added soon.
Furthermore, I encourage you to check out other interesting Python list tutorials on Statistics Globe, starting with these ones:
- Using Lists in Python
- Are Dictionaries Faster than Lists in Python?
- Append to 2D List in Python (3 Examples)
- Transpose 2D List in Python (3 Examples)
- Difference Between List & pandas DataFrame in Python
- Introduction to Python Programming
This post has shown, using two examples, how to find the index of duplicate elements in a list in Python. Your use case will determine which method to adopt.
I do hope you found this tutorial helpful! In case you have further questions, you may leave a comment below.
This page was created in collaboration with Ifeanyi Idiaye. You might check out Ifeanyi’s personal author page to read more about his academic background and the other articles he has written for the Statistics Globe website.
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