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Python Update Set Items

Last Updated : 06 Dec, 2024
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Python sets are a powerful data structure for storing unique, unordered items. While sets do not support direct item updating due to their unordered nature, there are several methods to update the contents of a set by adding or removing items. This article explores the different techniques for updating set items in Python.

Update Set item using update() Method

The update() method is used to add multiple items to a set. You can pass any iterable (such as a list, tuple, or another set) to the update() method.

Python
set = {1, 2, 3}
set.update([4, 5, 6])
print(set)  

In this example, the elements from the list [4, 5, 6] are added to the numbers set.

Let's take a look at other methods of updating set:

Using |= Operator (Union Assignment)

The |= operator performs an in-place union of the set with another iterable. This operation is equivalent to using update() method.

Python
set = {1, 2, 3}
set |= {4, 5, 6}
print(set)  # Output: {1, 2, 3, 4, 5, 6}

Here, the elements from the set {4, 5, 6} are added to the numbers set.

Using add() Method

The add() method allows you to add a single item to the set. This method is useful for updating the set with one item at a time.

Python
set1 = {1, 2, 3}
set1.add(4)
print(set1)  

In this example, the number 4 is added to the numbers set.

Removing Items with remove(), discard(), and pop()

Updating a set often involves removing items. Python provides several methods for this:

  • remove(item): Removes the specified item. Raises a KeyError if the item is not found.
  • discard(item): Removes the specified item. Does not raise an error if the item is not found.
  • pop(): Removes and returns an arbitrary item from the set. Raises a KeyError if the set is empty.
Python
set1 = {1, 2, 3, 4, 5}
set1.remove(3)
print(set1)  

set1.discard(2)
print(set1) 

item = set1.pop()
print(item)  
print(set1)  

Output
{1, 2, 4, 5}
{1, 4, 5}
1
{4, 5}

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