A python flatten function for arbitrarily nested arrays

flatten.py

def flatten(listOfLists):
	"""
  Flatten arbitrary levels of nesting for an array of integers.
  
  Any non list, non int value throws an exception.
  """
	results = []
  
  for item in listOfLists:
    if isinstance(item, int):
      results.append(item)
    if isinstance(item, list):
      for value in flatten(item):
        results.append(value)
    else:
      raise Exception("Not a list or integer: {}".format(item))
  return results

test.py

import unittest
from flatten import flatten

class TestFlatten(unittest.TestCase):
  def test_success(self):
    testList = [ 1, [1,2,[1,2,3]], 4, [234]]
    self.assertSequenceEqual(flatten(testList), [ 1,1,2,1,2,3,4,234 ])

  def test_fail(self):
    testList = [ 1, 4, ['abc']]
    with self.assertRaises(Exception):
      flatten(testList)

if __name__ == '__main__':
    unittest.main()