pydantic/pydantic · error · TypeError

Expected a class, got {type_param!r}

Error message

Expected a class, got {type_param!r}

What it means

Error "Expected a class, got {type_param!r}" thrown in pydantic/pydantic.

Source

Thrown at pydantic/_internal/_generate_schema.py:1757

            else:
                return self._type_schema()
        elif is_union_origin(get_origin(type_param)):
            return self._union_is_subclass_schema(type_param)
        else:
            if typing_objects.is_self(type_param):
                type_param = self._resolve_self_type(type_param)
            if _typing_extra.is_generic_alias(type_param):
                raise PydanticUserError(
                    'Subscripting `type[]` with an already parametrized type is not supported. '
                    f'Instead of using type[{type_param!r}], use type[{_repr.display_as_type(get_origin(type_param))}].',
                    code=None,
                )
            if not inspect.isclass(type_param):
                # when using type[None], this doesn't type convert to type[NoneType], and None isn't a class
                # so we handle it manually here
                if type_param is None:
                    return core_schema.is_subclass_schema(NoneType)
                raise TypeError(f'Expected a class, got {type_param!r}')
            return core_schema.is_subclass_schema(type_param)

    def _sequence_schema(self, items_type: Any) -> core_schema.CoreSchema:
        """Generate schema for a Sequence, e.g. `Sequence[int]`."""
        from ._serializers import serialize_sequence_via_list

        item_type_schema = self.generate_schema(items_type)
        list_schema = core_schema.list_schema(item_type_schema)

        json_schema = smart_deepcopy(list_schema)
        python_schema = core_schema.is_instance_schema(typing.Sequence, cls_repr='Sequence')
        if not typing_objects.is_any(items_type):
            from ._validators import sequence_validator

            python_schema = core_schema.chain_schema(
                [python_schema, core_schema.no_info_wrap_validator_function(sequence_validator, list_schema)],
            )

View on GitHub (pinned to 2e5f0e2b42)

When it happens

Trigger: Thrown at pydantic/_internal/_generate_schema.py:1757 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of pydantic/pydantic@2e5f0e2b42 (2026-08-04). Data as JSON: /data/errors/cf83c0b4cd8c4c48.json. Report an issue: GitHub.