freecodecamp--freecodecamp/curriculum/challenges/english/blocks/daily-coding-challenges-python/69162d64f96574d9bb629f02.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
69162d64f96574d9bb629f02	Challenge 117: Symmetric Difference	29	challenge-117

--description--

Given two arrays, return a new array containing the symmetric difference of them.

• The symmetric difference between two sets is the set of values that appear in either set, but not both.
• Return the values in the order they first appear in the input arrays.

--hints--

difference([1, 2, 3], [3, 4, 5]) should return [1, 2, 4, 5].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(difference([1, 2, 3], [3, 4, 5]), [1, 2, 4, 5])`)
}})

difference(["a", "b"], ["c", "b"]) should return ["a", "c"].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(difference(["a", "b"], ["c", "b"]), ["a", "c"])`)
}})

difference([1, "a", 2], [2, "b", "a"]) should return [1, "b"].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(difference([1, "a", 2], [2, "b", "a"]), [1, "b"])`)
}})

difference([1, 3, 5, 7, 9], [1, 2, 3, 4, 5, 6, 7, 8, 9]) should return [2, 4, 6, 8].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(difference([1, 3, 5, 7, 9], [1, 2, 3, 4, 5, 6, 7, 8, 9]), [2, 4, 6, 8])`)
}})

--seed--

--seed-contents--

def difference(arr1, arr2):

    return arr1

--solutions--

def difference(arr1, arr2):
    diff = []

    for v in arr1:
        if v not in arr2 and v not in diff:
            diff.append(v)

    for v in arr2:
        if v not in arr1 and v not in diff:
            diff.append(v)

    return diff