def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
def test_intarray_fields(self):
        class SomeInts(Structure):
            _fields_ = [("a", c_int * 4)]

        # can use tuple to initialize array (but not list!)
        self.assertEqual(SomeInts((1, 2)).a[:], [1, 2, 0, 0])
        self.assertEqual(SomeInts((1, 2)).a[::], [1, 2, 0, 0])
        self.assertEqual(SomeInts((1, 2)).a[::-1], [0, 0, 2, 1])
        self.assertEqual(SomeInts((1, 2)).a[::2], [1, 0])
        self.assertEqual(SomeInts((1, 2)).a[1:5:6], [2])
        self.assertEqual(SomeInts((1, 2)).a[6:4:-1], [])
        self.assertEqual(SomeInts((1, 2, 3, 4)).a[:], [1, 2, 3, 4])
        self.assertEqual(SomeInts((1, 2, 3, 4)).a[::], [1, 2, 3, 4])
        # too long
        # XXX Should raise ValueError?, not RuntimeError
        self.assertRaises(RuntimeError, SomeInts, (1, 2, 3, 4, 5))