quick and dirty quick sort in python

quick-sort.py

import random


def quick_sort(arr):
    if len(arr) <= 1:
        return arr

    pivot = arr[-1]
    pivot_index = len(arr) - 1

    i = -1
    for j in range(pivot_index + 1):
        # check if value at j < pivot
        # if true then: inc i by 1 and swap (i, j)
        if arr[j] < pivot:
            i += 1
            tmp = arr[i]
            arr[i] = arr[j]
            arr[j] = tmp

        if j == pivot_index:
            i += 1
            tmp = arr[i]
            arr[i] = arr[j]
            arr[j] = tmp
            pivot_index = i

    lhs = arr[:pivot_index]
    rhs = arr[pivot_index + 1:]

    return [*quick_sort(lhs), pivot, *quick_sort(rhs)]


numbers = [random.randint(0, 10_000) for _ in range(100)]
print(f'before: {numbers}')
numbers = quick_sort(numbers)
print(f'after: {numbers}')

if numbers != sorted(numbers):
    print('UNSORTED')
else:
    print('SORTED')