Sample python code to flatten an array of arbitrarily nested arrays of integers into a flat array of integers

flattenArray.py

"""
Author: Floyd Kots ~ github.com/floydkots

This module contains the flatten_array function
"""


def flatten_array(array):
    """
    Flatten an array of arbitrarily nested arrays of integers
    into a flat array of integers

    :param array: The nested array to flatten
    :return: A flat array of integers
    """
    if len(array) == 0:
        return []
    if len(array) == 1:
        return array
    flat_array = []
    for item in array:
        if isinstance(item, list):
            flat_array.extend(flatten_array(item))
        else:
            flat_array.append(item)
    return flat_array

flattenArrayTest.py

"""
Author: Floyd Kots ~ github.com/floydkots

This module contains unit tests to check the flatten_array function from flattenArray.py module
"""

from unittest import TestCase

from flattenArray import flatten_array


class FlattenArrayTest(TestCase):
    def testReturnsEmptyArray(self):
        self.assertEqual([], flatten_array([]))

    def testFlattensSingleItemArray(self):
        self.assertEqual([1], flatten_array([1]))

    def testFlattensSingleLevelArray(self):
        self.assertEqual([1, 2, 3], flatten_array([1, 2, 3]))

    def testFlattensTwoLevelNestedArray(self):
        self.assertEqual([1, 2, 3, 4], flatten_array([1, 2, [3, 4]]))

    def testFlattensThreeLevelNestedArray(self):
        self.assertEqual([1, 2, 3, 4, 5], flatten_array([[1, [2, 3]], 4, [5]]))

    def testFlattensGivenArray(self):
        self.assertEqual([1, 2, 3, 4], flatten_array([[1, 2, [3]], 4]))