# How To Remove Duplicates From The List In Python? So, first of all, when you think about this topic, “Removing duplicates from the list in Python”. There will be a lot of questions arising in your mind such as, “Why do we need to remove duplicates from the list?”, “What happens if we remove duplicates from the list?”, “How to remove duplicates from the list?”, “What are the ways to remove duplicates?”, etc. Am I right? So, by reading this article till the end, all your doubts and questions will be answered.

Do you know what means the duplicates in a list? Generally, duplicates are the integers or strings or any items in a list that are repeated more than one time. You will can such things as Duplicates in a list. Let me show you an example to make you clearly understand what are the duplicates in a list in Python.

Consider the following example of a list of integers:

list=[2,3,1,5,4,3,2,1].

Can you find the duplicates in the above list? Try to recognize them. Here, 2,3, and 1 are the duplicates in the given list because these integers are repeated more than once. Let us see an example program of this.

## Example:

``````list=[1,2,3,4,5,2,3,4,7,9,5]

list1=[]

for i in list:

if i not in list1:

list1.append(i)

else:

print(i,end=’ ‘)``````

If you run the above program in the editor, you will get the output as 2,3,4,5. Because these are the elements that are repeated more than once. Now, these four elements in the given list are known as duplicates.

To remove the duplicate elements from a given list, the primary thing is to find the duplicates in the list. The above program shows the method to find the duplicates in the list. So, let us see an explanation for the above Python program.

In the above Python program, the list included with some duplicate elements is taken to understand how to find the duplicates from a given list. In the code, we have taken an empty list (list1) where the non-duplicate elements of the given list are stored.

You can access the values in the list using a for loop as shown in the above program, and then you will use the “if condition” to check if the elements in the given list are present in the empty list (list1) or not.

The elements in the given list that are not repeated are stored in the empty list(list1) and the elements that have duplicate values are printed from the list. This is how you need to find the duplicate elements in the given list.

## Methods

You can use various methods for removing duplicates from the lists in the Python programming language. But, those methods depend upon the type of elements present in the list, the size of the list, whether the order of the elements should be preserved or not, and also depends on the efficiency of the removal approach. All these are iterative methods that use built-in functions for implementation, or they import modules for the functionality.

Usually, there are five different methods by which you will be able to remove the duplicates from the lists in the Python programming language. Now, I am going to describe all those methods individually.

The following are the list of methods you will use to remove duplicates from the given list:

## 1) Naive Method

The Naïve Method in Python programming language is also called an Iterative or a Temporary Method. This method is a basic approach for removing duplicates from a given list in Python programming language. Using this method, you will be able to iterate through the elements of the list. And it is also used to store the first occurrence of an element in a temporary list. However, here you will ignore any other occurrence of that particular element.

In the naive method, you can implement the basic approach by the following three steps:

1. First you have to traverse the list with the help of For-loop.
2. Then you have to add the elements to a temporary list if it is not already present in it.
3. Now, the final step is to assign the temporary list to the main list.

This is the basic approach to the implementation of the Naïve Method in Python.

Now, let’s look at an example program to understand the implementation of the Naive Method:

### Example-1:

``````#consider this as the main list

a = [10, 20, 10, 20, 20, 30, 30, 10, 80, 40,

100, 50, 60, 70, 80, 90, 40, 60, 90, 10]

#this is the temporary list which is empty

temp = []

# method to remove duplicates via Naive Method using For-loop

for integer in a:

if(integer not in temp):

temp.append(element)

# The below code assigns the temporary list to the main list

a = temp

print(“Unique List : “, a)``````

After running the above code in an editor, you will get the following Output:

Unique List :  [10, 20, 30, 80, 40, 100, 50, 60, 70, 90]

From the above example program, you will use the naive method in the keyword to check whether there is an integer in the temporary list or not. Therefore, only the unique integers are stored in the temporary list.

In this method, a temporary list is created to store unique elements. That is why an extra space is needed in this method while removing duplicates from the list.

## 2) List Comprehension

We have used the For-loop to implement the Naive method for removing duplicates from the list in the above example program. But, instead of that, you can also implement the Naive method in only one line of code using Python’s List comprehension functionality.

Now, let’s look at an example program to understand the implementation of the Naive Method using List comprehension.

Consider the following example:

### Example-2:

``````# consider this as the main list

a = [10, 20, 10, 20, 20, 30, 30, 10, 80, 40,

100, 50, 60, 70, 80, 90, 40, 60, 90, 10]

# this is the temporary list which is empty

temp = []

# method to remove duplicates via Naive Method using List comprehension

[temp.append(element) for element in a if element not in temp]

print(“Unique List : “, temp)``````

After running the above code in an editor, you will get the following Output:

Unique List :  [10, 20, 30, 80, 40, 100, 50, 60, 70, 90]

In this type of approach, you will initialize a temp variable where you can store the unique elements. Then, you can extract the unique elements from the input list using the list comprehension method.

The statement “[temp.append(element) for element in a if element not in temp]” in the above program indicates the following points:

You will use a for loop to iterate over the input list ‘a’. And using the if condition, you will be able to extract elements that are not present in the temp list with the help of the if condition.

You should add the extracted elements to the temp list with the help of List’s built-in append(element) function.a

## 3) List Comprehension + enumerate()

In this method, you will have to use both the list comprehension and enumerate() function. Using enumerate() function, you can iterate through a sequence by keeping the track of both the index and the element. When you are using the List comprehension method, you will store some distinct elements in a temporary list. But, when you are using the List comprehension method along with enumerate() function, the already occurred elements are skipped from adding to the temporary list.

Now, let’s look at an example program to understand the implementation of the Naive Method using List comprehension.

Consider the following example:

### Example-3:

``````# consider this as the main list

a = [10, 20, 10, 20, 20, 30, 30, 10, 80, 40,

100, 50, 60, 70, 80, 90, 40, 60, 90, 10]

# this is the temporary list which is empty

temp = []

# method to remove duplicates via List comprehension + enumerate()

temp = [element for index, element in enumerate(a) if element not in a[:index]]

print(“Unique List : “, temp)``````

After running the above code in an editor, you will get the following Output:

Unique List :  [10, 20, 30, 80, 40, 100, 50, 60, 70, 90]

## 4) list.count() + list.remove()

In this method, you will have to use both the ‘list.count()’ function and the‘ list.remove()’ function to remove the duplicates in the list in the python programming language. Both count() and remove() are known as the in-build functions in python language.

Let us see what happens when we use these functions:

1. The function ‘list.count’ is used to Return the number of occurrences of an element in the list.
2. The function ‘list.remove’ is used to remove the first occurrence of an element from the list.

Now, let’s look at an example program to understand the implementation of the Naive Method using List comprehension.

Consider the following example:

### Example-4:

``````# consider this as the main list

a = [10, 20, 10, 20, 20, 30, 30, 10, 80, 40,

100, 50, 60, 70, 80, 90, 40, 60, 90, 10]

# method to remove duplicates via list.count() + list.remove() method

for element in a[:]:

if (a.count(element) > 1):

a.remove(element)

print(“Unique List : “, a)``````

After running the above code in an editor, you will get the following Output:

Unique List :  [20, 30, 100, 50, 70, 80, 40, 60, 90, 10]

## Bottom Line

Therefore, I conclude that you can remove duplicates from a python list using the above-described methods. You easily use those methods if you are able to understand them. Try to learn all these methods so that you won’t face any issues while writing programs related to removing duplicates in the Python programming language. And if you face any problem doing this, you can contact us any time to get help with your assignments.

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