How Can I Find the Common Elements Between Two Lists in Python?

Combining Elements Shared Between Lists

Determining the common elements between two lists is a prevalent task in programming. Suppose you have two lists containing distinct values and need to identify the overlapping items they share. This article will demonstrate how to compute the intersection of two lists using Python's set intersection operation.

To begin, you must convert the input lists into sets using Python's set() function. A set is an unordered collection that stores unique elements. Once you have created sets for both lists, use the intersection() method to find their common elements. The result is another set containing all the values that appear in both input sets.

For instance, if you have the lists [1, 2, 3, 4, 5, 6] and [3, 5, 7, 9], converting them to sets would yield {1, 2, 3, 4, 5, 6} and {3, 5, 7, 9}. Applying the intersection() operation to these sets would result in the set {3, 5}, which contains the common elements between the original lists.

This technique can be extended to comparing lists of strings, as demonstrated by the example ['this', 'this', 'n', 'that'] and ['this', 'not', 'that', 'that']. Converting them to sets would produce {this, n, that} and {this, not, that}. Computing their intersection would give you the set {this, that}, containing the shared elements 'this' and 'that'.

The set intersection operation is a versatile tool for finding common elements in lists and can be easily applied to any number of lists, whether they contain numeric or string values.

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