BaseChatMessageHistory#

class langchain_core.chat_history.BaseChatMessageHistory[source]#

Abstract base class for storing chat message history.

Implementations guidelines:

Implementations are expected to over-ride all or some of the following methods:

add_messages: sync variant for bulk addition of messages
aadd_messages: async variant for bulk addition of messages
messages: sync variant for getting messages
aget_messages: async variant for getting messages
clear: sync variant for clearing messages
aclear: async variant for clearing messages

add_messages contains a default implementation that calls add_message for each message in the sequence. This is provided for backwards compatibility with existing implementations which only had add_message.

Async variants all have default implementations that call the sync variants. Implementers can choose to over-ride the async implementations to provide truly async implementations.

Usage guidelines:

When used for updating history, users should favor usage of add_messages over add_message or other variants like add_user_message and add_ai_message to avoid unnecessary round-trips to the underlying persistence layer.

Example: Shows a default implementation.

import json
import os
from langchain_core.messages import messages_from_dict, message_to_dict


class FileChatMessageHistory(BaseChatMessageHistory):
    storage_path: str
    session_id: str

    @property
    def messages(self) -> list[BaseMessage]:
        try:
            with open(
                os.path.join(self.storage_path, self.session_id),
                "r",
                encoding="utf-8",
            ) as f:
                messages_data = json.load(f)
            return messages_from_dict(messages_data)
        except FileNotFoundError:
            return []

    def add_messages(self, messages: Sequence[BaseMessage]) -> None:
        all_messages = list(self.messages)  # Existing messages
        all_messages.extend(messages)  # Add new messages

        serialized = [message_to_dict(message) for message in all_messages]
        file_path = os.path.join(self.storage_path, self.session_id)
        os.makedirs(os.path.dirname(file_path), exist_ok=True)
        with open(file_path, "w", encoding="utf-8") as f:
            json.dump(serialized, f)

    def clear(self) -> None:
        file_path = os.path.join(self.storage_path, self.session_id)
        os.makedirs(os.path.dirname(file_path), exist_ok=True)
        with open(file_path, "w", encoding="utf-8") as f:
            json.dump([], f)

Attributes

Methods

`aadd_messages`(messages)	Async add a list of messages.
`aclear`()	Async remove all messages from the store.
`add_ai_message`(message)	Convenience method for adding an AI message string to the store.
`add_message`(message)	Add a Message object to the store.
`add_messages`(messages)	Add a list of messages.
`add_user_message`(message)	Convenience method for adding a human message string to the store.
`aget_messages`()	Async version of getting messages.
`clear`()	Remove all messages from the store.

async aadd_messages( messages: Sequence[BaseMessage], ) → None[source]#

Async add a list of messages.

Parameters:: messages (Sequence[BaseMessage]) – A sequence of BaseMessage objects to store.
Return type:: None

async aclear() → None[source]#

Async remove all messages from the store.

Return type:: None

add_ai_message( message: AIMessage | str, ) → None[source]#

Convenience method for adding an AI message string to the store.

Note

This is a convenience method. Code should favor the bulk add_messages interface instead to save on round-trips to the persistence layer.

This method may be deprecated in a future release.

Parameters:: message (AIMessage | str) – The AI message to add.
Return type:: None

add_message( message: BaseMessage, ) → None[source]#

Add a Message object to the store.

Parameters:: message (BaseMessage) – A BaseMessage object to store.
Raises:: NotImplementedError – If the sub-class has not implemented an efficient add_messages method.
Return type:: None

add_messages( messages: Sequence[BaseMessage], ) → None[source]#

Add a list of messages.

Implementations should over-ride this method to handle bulk addition of messages in an efficient manner to avoid unnecessary round-trips to the underlying store.

Parameters:: messages (Sequence[BaseMessage]) – A sequence of BaseMessage objects to store.
Return type:: None

add_user_message( message: HumanMessage | str, ) → None[source]#

Convenience method for adding a human message string to the store.

Note

This is a convenience method. Code should favor the bulk add_messages interface instead to save on round-trips to the persistence layer.

This method may be deprecated in a future release.

Parameters:: message (HumanMessage | str) – The human message to add to the store.
Return type:: None

async aget_messages() → list[BaseMessage][source]#

Async version of getting messages.

Can over-ride this method to provide an efficient async implementation.

In general, fetching messages may involve IO to the underlying persistence layer.

Returns:: The messages.
Return type:: list[BaseMessage]

abstractmethod clear() → None[source]#

Remove all messages from the store.

Return type:: None

Examples using BaseChatMessageHistory