def test_negative_step(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers, step=-1)
self.assertEqual(list(view), [18, 11, 7, 4, 3, 1, 2])
view = SliceView(numbers, stop=1, step=-2)
self.assertEqual(list(view), [18, 7, 3])
view = SliceView(numbers, start=4, stop=1, step=-2)
self.assertEqual(list(view), [7, 3])
def test_has_length(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
self.assertEqual(len(SliceView(numbers, stop=4)), 4)
self.assertEqual(len(SliceView(numbers, start=2)), 5)
self.assertEqual(len(SliceView(numbers, start=1, stop=5)), 4)
self.assertEqual(len(SliceView(numbers, start=-3)), 3)
self.assertEqual(len(SliceView(numbers, stop=-2)), 5)
self.assertEqual(len(SliceView(numbers, start=-100)), 7)
self.assertEqual(len(SliceView(numbers, stop=100)), 7)
self.assertEqual(len(SliceView(numbers, step=-1)), 7)
self.assertEqual(len(SliceView(numbers, stop=1, step=-2)), 3)
def test_no_start_or_stop(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers)
self.assertEqual(list(view), numbers)
self.assertIsNot(view, numbers)
self.assertNotEqual(type(view), list)
self.assertNotEqual(type(view), tuple)
def test_slicing_and_indexing(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers)
self.assertEqual(list(view[2:]), [3, 4, 7, 11, 18])
self.assertEqual(list(view[:-1]), [2, 1, 3, 4, 7, 11])
self.assertEqual(list(view[::-1]), [18, 11, 7, 4, 3, 1, 2])
self.assertEqual(type(view[::-1]), SliceView)
self.assertEqual(view[::-1][1], 11)
self.assertEqual(view[::-1][-2], 1)
def test_does_not_slice_sequence(self):
class UnsliceableList(list):
def __getitem__(self, index):
if not isinstance(index, int):
return NotImplemented
return super().__getitem__(index)
numbers = UnsliceableList([2, 1, 3, 4, 7, 11, 18])
view = SliceView(numbers, stop=5)
self.assertEqual(list(view), [2, 1, 3, 4, 7])
def test_no_memory_used(self):
numbers = range(1000000)
view = SliceView(numbers, start=1, stop=5)
if isinstance(view, Generator):
next(view)
size = sum(
sys.getsizeof(obj) for obj in view.gi_frame.f_locals.values())
else:
size = sys.getsizeof(view)
self.assertLess(size, 8000, 'Too much memory used')
self.assertNotEqual(type(view), list)
self.assertNotEqual(type(view), tuple)
def test_looping_multiple_times(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers, start=2)
self.assertEqual(list(view), [3, 4, 7, 11, 18])
self.assertEqual(list(view), [3, 4, 7, 11, 18])
def test_out_of_range(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers, start=-100)
self.assertEqual(list(view), [2, 1, 3, 4, 7, 11, 18])
view = SliceView(numbers, stop=100)
self.assertEqual(list(view), [2, 1, 3, 4, 7, 11, 18])
def test_negative_stop(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers, stop=-2)
self.assertEqual(list(view), [2, 1, 3, 4, 7])
def test_negative_start(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers, start=-3)
self.assertEqual(list(view), [7, 11, 18])
def test_start_and_stop(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers, start=1, stop=5)
self.assertEqual(list(view), [1, 3, 4, 7])
def test_start_but_no_stop(self):
numbers = [2, 1, 3, 4, 7, 11, 18]
view = SliceView(numbers, start=2)
self.assertEqual(list(view), [3, 4, 7, 11, 18])