How To Remove Duplicates From List
Python Tutorials
How to Remove Duplicates from a List in Python
You can remove duplicates from a Python using the dict.fromkeys(), which generates a lexicon that removes whatsoever duplicate values. You lot can also convert a list to a gear up. You must convert the dictionary or set back into a listing to come across a listing whose duplicates have been removed.
When yous're working with a list in Python, there may be a scenario where you desire to remove duplicates from the list. For example, say yous are a chef who is merging the old and new menus for your restaurant. You lot may want to remove whatever duplicates that occur from combining the 2 menus.
This tutorial volition embrace using the dict.fromkeys() method converting a list to a set. Nosotros'll talk over how to convert the output from these ii methods back into a list so you can interpret your data as a list.
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Python Remove Duplicates From a List
You lot tin can remove duplicates using a Python set or the dict.fromkeys() method.
The dict.fromkeys() method converts a list into a dictionary. Dictionaries cannot comprise indistinguishable values so a dictionary with only unique values is returned past dict.fromkeys().
Sets, like dictionaries, cannot incorporate duplicate values. If nosotros convert a list to a set, all the duplicates are removed.
Python Remove Duplicates from Listing: dict.fromkeys()
Python dictionaries store data in a central/value construction. Dictionaries map keys to values and create a pair that stores data in Python.
Dictionaries in Python cannot include duplicate keys. If we convert our list to a dictionary, it will remove whatsoever duplicate values. That's where the fromkeys() method comes in.
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dict.fromkeys() Example
fromkeys() is a built-in role that generates a dictionary from the keys you have specified. Because dictionaries cannot include duplicate keys, the office will remove any duplicate values from our list. So, we tin catechumen our dictionary back to a listing.
The syntax for the fromkeys() method is as follows:
dictionary_name.fromkeys(keys, value)
fromkeys takes two parameters: keys and value. The keys parameter is the iterable, which specifies the keys of the new dictionary you want to create. Our value parameter is optional and holds the value for all keys. We do not demand this parameter for this example, then we will ignore it.
Let's say that we are a chef who is merging the erstwhile and new pizza menus into one big card. The new menu includes a number of new pizzas that nosotros take been working on for months. Merely, nosotros want to offering the pizzas on the old menu. We exercise not want duplicates to appear on the carte du jour, because that would confuse customers.
To remove whatsoever duplicates that may exist in the new menu, we could use the following code:
new_menu = ['Hawaiian', 'Margherita', 'Mushroom', 'Prosciutto', 'Meat Feast', 'Hawaiian', 'Bacon', 'Black Olive Special', 'Sausage', 'Sausage'] final_new_menu = list(dict.fromkeys(new_menu)) print(final_new_menu)
Our code removes our duplicated elements and returns:
['Hawaiian', 'Margherita', 'Mushroom', 'Prosciutto', 'Meat Banquet', 'Salary', 'Black Olive Special', 'Sausage']
On the first line, nosotros declare a Python variable chosen new_menu which stores all the pizzas on the new menu. Note that this list contains duplicate values — both Sausage and Hawaiian announced twice in the Python lists.
We use the dict.fromkeys() method to create a dictionary from our new_menu variable. Adjacent, nosotros use list() to catechumen our data from a lexicon to a Python array , or list. On the final line of code, we impress out our revised list.
As y'all tin can see, our program has removed the duplicate values from our data, and Sausage and Hawaiian appear once in our new listing.
Remove Duplicates from List Python: Sets
The Python set object is a data structure that is both unordered and unindexed . Sets shop collections of unique items in Python. Unlike lists, sets cannot store duplicate values.
So, because sets cannot shop indistinguishable items, we can convert our list to a set to remove them. In Python, sets are a listing of comma-separated items enclosed within curly brackets. Here'south an example of a set in Python that stores a list of pizzas:
pizzas = ('Margherita', 'Hawaiian', 'Mushroom', 'Meat Feast') Remove Duplicates Using a Set Case
Let'southward take our example from higher up to illustrate how sets can be used to remove duplicate values from a list.
Say that we are a pizza chef who wants to merge both our former and new menus. Only there may exist duplicates betwixt these menus, which we will want to remove before creating our final card. To remove these duplicates using the ready approach, we could utilize the following code:
new_menu = ['Hawaiian', 'Margherita', 'Mushroom', 'Prosciutto', 'Meat Banquet', 'Hawaiian', 'Bacon', 'Black Olive Special', 'Sausage', 'Sausage'] final_new_menu = listing(set(new_menu)) print(final_new_menu)
Here'due south our list afterward removing duplicate values:
['Mushroom', 'Black Olive Special', 'Meat Feast', 'Salary', 'Margherita', 'Sausage', 'Prosciutto', 'Hawaiian']
At the beginning of our plan, nosotros declare a listing chosen new_menu which stores all the pizzas on the new carte du jour.
Then, we declare a variable called final_new_menu which stores our revised menu. This variable converts the new_menu variable to a ready using ready() , then converts the set dorsum to a list using list() . This process removes all the duplicate values in our new_menu variable.
Finally, our plan prints the new menu to the console. All the unique elements from the original list object appear. We now have a unique listing.
Determination
Removing duplicate items from a list is a common operation in Python. There is no official method that should exist used to remove duplicates from a list. The almost common approaches are to apply the dictionary fromkeys() function or convert your information into a set.
In this guide, we discussed how to use the dictionary fromkeys() function and sets to remove duplicates from a list in Python.
To larn more about Python programming, read our How to Learn Python guide .
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