Method __init__

lib/sqlalchemy/sql/schema.py:4224–4263

(
        self,
        *columns: _DDLColumnArgument,
        _autoattach: bool = True,
        _column_flag: bool = False,
        _gather_expressions: Optional[
            List[Union[str, ColumnElement[Any]]]
        ] = None,
    )

        ) -> None: ...

    def __init__(
        self,
        *columns: _DDLColumnArgument,
        _autoattach: bool = True,
        _column_flag: bool = False,
        _gather_expressions: Optional[
            List[Union[str, ColumnElement[Any]]]
        ] = None,
    ) -> None:
        self._column_flag = _column_flag
        self._columns = DedupeColumnCollection()

        processed_expressions: Optional[
            List[Union[ColumnElement[Any], str]]
        ] = _gather_expressions

        if processed_expressions is not None:

            # this is expected to be an empty list
            assert not processed_expressions

            self._pending_colargs = []
            for (
                expr,
                _,
                _,
                add_element,
            ) in coercions.expect_col_expression_collection(
                roles.DDLConstraintColumnRole, columns
            ):
                self._pending_colargs.append(add_element)
                processed_expressions.append(expr)
        else:
            self._pending_colargs = [
                coercions.expect(roles.DDLConstraintColumnRole, column)
                for column in columns
            ]

        if _autoattach and self._pending_colargs:
            self._check_attach()

    def _check_attach(self, evt: bool = False) -> None:
        col_objs = [c for c in self._pending_colargs if isinstance(c, Column)]