def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def test_emtpy(self):
        # I had problems with these
        #
        # Although these are patological cases: Empty Structures!
        class X(Structure):
            _fields_ = []

        class Y(Union):
            _fields_ = []

        # Is this really the correct alignment, or should it be 0?
        self.assertTrue(alignment(X) == alignment(Y) == 1)
        self.assertTrue(sizeof(X) == sizeof(Y) == 0)

        class XX(Structure):
            _fields_ = [("a", X),
                        ("b", X)]

        self.assertEqual(alignment(XX), 1)
        self.assertEqual(sizeof(XX), 0)