Python .difference_update()

In Python, the .difference_update() method modifies a set by removing all elements present in another set, keeping only the ones that are not found in the other one. Unlike the .difference() method, which returns a new set, .difference_update() changes the original set in place.

Syntax

set.difference_update(set1, set2, ..., setN)

• set: The set to be modified.
• set1, set2, ..., setN: The set(s) whose elements are to be removed from the original set.

Example

In this example, the set salad is modified using the .difference_update() method to remove elements also present in the larder set. After the operation, the salad set will only contain elements not found in the larder set:

salad = {'lettuce', 'beetroot', 'walnuts', 'cheese', 'seeds'}
larder = {'tomatoes', 'lettuce', 'cheese', 'seeds', 'celery'}

salad.difference_update(larder)
print(salad)

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The above example produces the following output:

{'walnuts', 'beetroot'}

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Codebyte Example

In the below codebyte example, the salad set has elements removed if they are found in larder, shopping1, or shopping2 sets, leaving unique elements in the salad set:

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