Python List Intersection | Programming Tutorials | Challenge

Introduction

In Python, we can find the intersection of two lists using the set() and intersection() methods. However, what if we want to find the intersection based on a specific function applied to each element in both lists? In this challenge, you will create a function that takes in two lists and a function, and returns a list of elements that exist in both lists, after applying the provided function to each list element of both.

Skills Graph

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List Intersection Based on Function

Problem

Write a function intersection_by(a, b, fn) that takes in two lists a and b, and a function fn. The function should return a list of elements that exist in both lists, after applying the provided function to each list element of both.

Input

Two lists a and b (1 <= len(a), len(b) <= 1000)

A function fn that takes in one argument and returns a value

Output

A list of elements that exist in both lists, after applying the provided function to each list element of both.

Example

intersection_by([2.1, 1.2], [2.3, 3.4], floor) ## [2.1]

Note

In the example above, the function floor() is applied to each element in both lists. The resulting sets are {2, 3} and {2, 1}. The intersection of these sets is {2}, which is then returned as a list.

Summary

In this challenge, you have learned how to find the intersection of two lists based on a specific function applied to each element in both. You have written a function intersection_by(a, b, fn) that takes in two lists and a function, and returns a list of elements that exist in both lists, after applying the provided function to each list element of both.

List Intersection Based on Function | Challenge