Method test_batched

Lib/test/test_itertools.py:160–200

(self)

            list(accumulate([10, 20], 100))

    def test_batched(self):
        self.assertEqual(list(batched('ABCDEFG', 3)),
                             [('A', 'B', 'C'), ('D', 'E', 'F'), ('G',)])
        self.assertEqual(list(batched('ABCDEFG', 2)),
                             [('A', 'B'), ('C', 'D'), ('E', 'F'), ('G',)])
        self.assertEqual(list(batched('ABCDEFG', 1)),
                            [('A',), ('B',), ('C',), ('D',), ('E',), ('F',), ('G',)])
        self.assertEqual(list(batched('ABCDEF', 2, strict=True)),
                             [('A', 'B'), ('C', 'D'), ('E', 'F')])

        with self.assertRaises(ValueError):         # Incomplete batch when strict
            list(batched('ABCDEFG', 3, strict=True))
        with self.assertRaises(TypeError):          # Too few arguments
            list(batched('ABCDEFG'))
        with self.assertRaises(TypeError):
            list(batched('ABCDEFG', 3, None))       # Too many arguments
        with self.assertRaises(TypeError):
            list(batched(None, 3))                  # Non-iterable input
        with self.assertRaises(TypeError):
            list(batched('ABCDEFG', 'hello'))       # n is a string
        with self.assertRaises(ValueError):
            list(batched('ABCDEFG', 0))             # n is zero
        with self.assertRaises(ValueError):
            list(batched('ABCDEFG', -1))            # n is negative

        data = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
        for n in range(1, 6):
            for i in range(len(data)):
                s = data[:i]
                batches = list(batched(s, n))
                with self.subTest(s=s, n=n, batches=batches):
                    # Order is preserved and no data is lost
                    self.assertEqual(''.join(chain(*batches)), s)
                    # Each batch is an exact tuple
                    self.assertTrue(all(type(batch) is tuple for batch in batches))
                    # All but the last batch is of size n
                    if batches:
                        last_batch = batches.pop()
                        self.assertTrue(all(len(batch) == n for batch in batches))
                        self.assertTrue(len(last_batch) <= n)
                        batches.append(last_batch)

    def test_chain(self):