Python typing 模块，ClassVar() 实例源码

def create_typed_numpy_ndarray(
        dims: int, data_type: t.ClassVar, required_shape: t.Optional[t.Sequence[int]] = None):
    """Create a statically typed version of numpy.ndarray."""

    def typed_ndarray(*args, **kwargs):
        """Create an instance of numpy.ndarray which must conform to declared type constraints."""

        shape_loc = (args, 0) if len(args) > 0 else (kwargs, 'shape')
        dtype_loc = (args, 1) if len(args) > 1 else (kwargs, 'dtype')

        shape = shape_loc[0][shape_loc[1]]
        if shape is not None and (dims != 1 if isinstance(shape, int) else len(shape) != dims):
            raise ValueError(
                'actual ndarray shape {} conflicts with its declared dimensionality of {}'
                .format(shape, dims))

        if required_shape is not None:
            if any((req_dim is not Ellipsis and dim != req_dim)
                   for dim, req_dim in zip(shape, required_shape)):
                raise ValueError('actual ndarray shape {} conflicts with its required shape of {}'
                                 .format(shape, required_shape))

        try:
            dtype = dtype_loc[0][dtype_loc[1]]
        except KeyError:
            dtype = None
        if dtype is not None and dtype is not data_type:
            raise TypeError('actual ndarray dtype {} conflicts with its declared dtype {}'
                            .format(dtype, data_type))
        dtype_loc[0][dtype_loc[1]] = data_type

        # print('np.ndarray', args, kwargs)
        return np.ndarray(*args, **kwargs)

    return typed_ndarray