Reducers¶

Merge the updates of nodes into state fields. See State.

Name	What it is
Merge functions
`add`	Reducer that appends the items of a list update to a list.
`add_messages`	Reducer that appends chat messages and edits or removes them by id.
`merge_dict`	Reducer that merges the top-level keys of a dict update into a dict.
`replace`	Reducer that keeps the new value.
Update values
`RemoveMessage`	An `add_messages` update item that removes the message with `id`.
`Replace`	An update value that sets a field directly, bypassing its reducer.

Merge functions¶

add¶

add(current, update) -> list[Any]

Reducer that appends the items of a list update to a list.

Parameters
`current`	`Any`	The field's value, or None when the field has no value yet.
`update`	`Any`	Items to append; a single item must be wrapped in a list.

Returns
`list`	A new list.

Raises
`TypeError`	If `update` is not a list, or `current` is neither a list nor None.

add_messages¶

add_messages(current, update) -> list[Any]

Reducer that appends chat messages and edits or removes them by id.

A message whose id is already in the list replaces that message in place, a RemoveMessage removes the message with its id, and every other message is appended. Messages without an id get a new one.

Parameters
`current`	`Any`	The field's value, or None when the field has no value yet.
`update`	`Any`	Chat messages and `RemoveMessage` items.

Returns
`list`	A new list.

Raises
`TypeError`	If `update` is not a list, or holds an item that is neither a chat message nor a `RemoveMessage`.
`StateUpdateError`	If two items of `update` have the same id, or a `RemoveMessage` names an id that is not in `current`.

merge_dict¶

merge_dict(current, update) -> dict[Any, Any]

Reducer that merges the top-level keys of a dict update into a dict.

replace¶

replace(current, update) -> Any

Reducer that keeps the new value.

Update values¶

RemoveMessage¶

RemoveMessage(id)

An add_messages update item that removes the message with id.

Works in node updates, Command.update, Graph.update_state and input on an existing thread.

Parameters
`id`	`str`	Id of the message to remove.

Examples

>>> from nodestep import RemoveMessage
>>> update = {"messages": [RemoveMessage("m1")]}

Replace¶

Replace(value)

An update value that sets a field directly, bypassing its reducer.

Works in node updates, Command.update, Graph.update_state and run input, not in Send payloads.

Parameters
`value`	`Any`	The field's new value.

Examples

>>> from nodestep import Replace
>>> update = {"messages": Replace([])}