Testing if two lists are equal regardless of the order of the objects in it

Question

Is there a way to check if two lists are equal, depending on the values in it but regardless of their order.

for example:

[3,4,5] == [5,3,4] will be: true

You can of course sort the 2 lists and then compare them, the question is whether it is possible to check if lists are equal using their values, without sorting them

If the values are all hashable, then keeping the two collections as sets instead of lists would be the simplest answer. (There might be some issues if duplicate values are possible.) — jasonharper, Sep 18 '22 at 17:05
Sets will do for most applications but note that sets can't hold the same element more than once. — Joooeey, Sep 18 '22 at 17:07
Having committed the ultimate blooper by not reading the entire question, I'm left with the question, Why? What is the scenario, where using `sort` is not applicable? — Rolf of Saxony, Sep 18 '22 at 17:20

score 7 · Accepted Answer · answered Sep 18 '22 at 17:11

7

You can use Counter from collections

Counter(listA) == Counter(listB)

or if you want to sort them

sorted(listA) == sorted(listB)

answered Sep 18 '22 at 17:11

Milos Bogdanovic

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1
6

`Counter(listA) == Counter(listB)` looks great! – Talha Tayyab Sep 18 '22 at 17:16

score 2 · Answer 2 · answered Sep 18 '22 at 17:10

If you don't want to sort, then compare the quantities of the present elements of each in the form of a dictionary using Counter from python's collections library.

from collections import Counter

def check_equal_without_sort(arr1, arr2):
    return Counter(arr1) == Counter(arr2)

arr1 = [3,4,5]
arr2 = [5,3,4]
print(check_equal_without_sort(arr1,arr2))

Testing if two lists are equal regardless of the order of the objects in it

2 Answers2