Function iterate

lib/sqlalchemy/sql/visitors.py:806–844

r"""Traverse the given expression structure, returning an iterator. Traversal is configured to be breadth-first. The central API feature used by the :func:`.visitors.iterate` function is the :meth:`_expression.ClauseElement.get_children` method of :class:`_expression.ClauseElem

(
    obj: Optional[ExternallyTraversible],
    opts: Mapping[str, Any] = util.EMPTY_DICT,
)

def iterate(
    obj: Optional[ExternallyTraversible],
    opts: Mapping[str, Any] = util.EMPTY_DICT,
) -> Iterator[ExternallyTraversible]:
    r"""Traverse the given expression structure, returning an iterator.

    Traversal is configured to be breadth-first.

    The central API feature used by the :func:`.visitors.iterate`
    function is the
    :meth:`_expression.ClauseElement.get_children` method of
    :class:`_expression.ClauseElement` objects.  This method should return all
    the :class:`_expression.ClauseElement` objects which are associated with a
    particular :class:`_expression.ClauseElement` object. For example, a
    :class:`.Case` structure will refer to a series of
    :class:`_expression.ColumnElement` objects within its "whens" and "else\_"
    member variables.

    :param obj: :class:`_expression.ClauseElement` structure to be traversed

    :param opts: dictionary of iteration options.   This dictionary is usually
     empty in modern usage.

    """
    if obj is None:
        return

    yield obj
    children = obj.get_children(**opts)

    if not children:
        return

    stack = deque([children])
    while stack:
        t_iterator = stack.popleft()
        for t in t_iterator:
            yield t
            stack.append(t.get_children(**opts))


@overload