Method test_tee

Lib/test/test_itertools.py:1223–1336

(self)

    @unittest.expectedFailure  # TODO: RUSTPYTHON
    def test_tee(self):
        n = 200

        a, b = tee([])        # test empty iterator
        self.assertEqual(list(a), [])
        self.assertEqual(list(b), [])

        a, b = tee(irange(n)) # test 100% interleaved
        self.assertEqual(lzip(a,b), lzip(range(n), range(n)))

        a, b = tee(irange(n)) # test 0% interleaved
        self.assertEqual(list(a), list(range(n)))
        self.assertEqual(list(b), list(range(n)))

        a, b = tee(irange(n)) # test dealloc of leading iterator
        for i in range(100):
            self.assertEqual(next(a), i)
        del a
        self.assertEqual(list(b), list(range(n)))

        a, b = tee(irange(n)) # test dealloc of trailing iterator
        for i in range(100):
            self.assertEqual(next(a), i)
        del b
        self.assertEqual(list(a), list(range(100, n)))

        for j in range(5):   # test randomly interleaved
            order = [0]*n + [1]*n
            random.shuffle(order)
            lists = ([], [])
            its = tee(irange(n))
            for i in order:
                value = next(its[i])
                lists[i].append(value)
            self.assertEqual(lists[0], list(range(n)))
            self.assertEqual(lists[1], list(range(n)))

        # test argument format checking
        self.assertRaises(TypeError, tee)
        self.assertRaises(TypeError, tee, 3)
        self.assertRaises(TypeError, tee, [1,2], 'x')
        self.assertRaises(TypeError, tee, [1,2], 3, 'x')

        # tee object should be instantiable
        a, b = tee('abc')
        c = type(a)('def')
        self.assertEqual(list(c), list('def'))

        # test long-lagged and multi-way split
        a, b, c = tee(range(2000), 3)
        for i in range(100):
            self.assertEqual(next(a), i)
        self.assertEqual(list(b), list(range(2000)))
        self.assertEqual([next(c), next(c)], list(range(2)))
        self.assertEqual(list(a), list(range(100,2000)))
        self.assertEqual(list(c), list(range(2,2000)))

        # test values of n