# intersection_update () in Python for finding common elements in n arrays

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Examples:

` Input: arr = [[1,2,3,4], [8,7,3,2], [9,2,6,3], [5, 1,2,3]] Output: Common Elements = [2,3] `

We can quickly solve this problem in python with the intersection_update () Set () data structures .

How does intersection_update () work?

Suppose we have two sets A and B, then operation A.intersection_update (B) updates set A with common elements in sets A and B. For example, A = set ([1,2,3]) and B = set ([4,2,3]) now after accepting A.intersection_update (B) , the value of set A will be [2,3]. Syntax anySet.intersection_update (iterable) .

 ` # Function for finding common elements in n arrays ` ` def ` ` commonElements (arr): ` ` # initialize the result with the first array as a set ` ` result ` ` = ` ` set ` ` (arr [` ` 0 ` `]) ` ` # now iterate over the list of arrays, starting c ` ` # second array and take intersection_update () from ` ` # each array with the result. Each operation will ` ` # update the result value with shared values ‚Äã‚Äãin ` ` # result set and overlap set ` ` for ` ` currSet ` ` in ` ` arr [` ` 1 ` `:]: ` ` ` ` result.intersection_update (currSet) ` ` return ` ` list ` ` (result) ` ` # Driver code ` ` if ` ` __ name__ ` ` = ` ` = ` ` "__ main__" ` `: ` ` arr ` ` = ` ` [[` ` 1 ` `, ` ` 2 ` `, ` ` 3 ` `, ` ` 4 ` `], [` ` 8 ` `, ` ` 7 ` `, ` ` 3 ` `, ` ` 2 ` `], [` ` 9 ` `, ` ` 2 ` `, ` ` 6 ` `, ` ` 3 ` `], [` ` 5 ` `, ` ` 1 ` `, ` ` 2 ` `, ` ` 3 ` `]] ` ` output ` ` = ` ` commonElements (arr) ` ` if ` ` len ` ` (output) & gt; ` ` 0 ` `: ` ` print ` ` output ` ` else ` `: ` ` print ` ` ’No Common Elements Found’ `

Output:

` Common Elements = [2,3] `

This article is courtesy of Shashank Mishra (Gullu) . If you are as Python.Engineering and would like to contribute, you can also write an article using contribute.python.engineering or by posting an article contribute @ python.engineering. See my article appearing on the Python.Engineering homepage and help other geeks.

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