Storage¶

langchain-classic documentation

These docs cover the langchain-classic package. This package will be maintained for security vulnerabilities until December 2026. Users are encouraged to migrate to the langchain package for the latest features and improvements. See docs for langchain

langchain_classic.storage ¶

Implementations of key-value stores and storage helpers.

Module provides implementations of various key-value stores that conform to a simple key-value interface.

The primary goal of these storages is to support implementation of caching.

EncoderBackedStore ¶

Bases: BaseStore[K, V]

Wraps a store with key and value encoders/decoders.

Examples that uses JSON for encoding/decoding:

import json


def key_encoder(key: int) -> str:
    return json.dumps(key)


def value_serializer(value: float) -> str:
    return json.dumps(value)


def value_deserializer(serialized_value: str) -> float:
    return json.loads(serialized_value)


# Create an instance of the abstract store
abstract_store = MyCustomStore()

# Create an instance of the encoder-backed store
store = EncoderBackedStore(
    store=abstract_store,
    key_encoder=key_encoder,
    value_serializer=value_serializer,
    value_deserializer=value_deserializer,
)

# Use the encoder-backed store methods
store.mset([(1, 3.14), (2, 2.718)])
values = store.mget([1, 2])  # Retrieves [3.14, 2.718]
store.mdelete([1, 2])  # Deletes the keys 1 and 2

METHOD	DESCRIPTION
`__init__`	Initialize an `EncodedStore`.
`mget`	Get the values associated with the given keys.
`amget`	Async get the values associated with the given keys.
`mset`	Set the values for the given keys.
`amset`	Async set the values for the given keys.
`mdelete`	Delete the given keys and their associated values.
`amdelete`	Async delete the given keys and their associated values.
`yield_keys`	Get an iterator over keys that match the given prefix.
`ayield_keys`	Async get an iterator over keys that match the given prefix.

init ¶

__init__(
    store: BaseStore[str, Any],
    key_encoder: Callable[[K], str],
    value_serializer: Callable[[V], bytes],
    value_deserializer: Callable[[Any], V],
) -> None

Initialize an EncodedStore.

PARAMETER	DESCRIPTION
`store`	The underlying byte store to wrap. TYPE: `BaseStore[str, Any]`
`key_encoder`	Function to encode keys from type `K` to strings. TYPE: `Callable[[K], str]`
`value_serializer`	Function to serialize values from type `V` to bytes. TYPE: `Callable[[V], bytes]`
`value_deserializer`	Function to deserialize bytes back to type V. TYPE: `Callable[[Any], V]`

mget ¶

mget(keys: Sequence[K]) -> list[V | None]

Get the values associated with the given keys.

PARAMETER	DESCRIPTION
`keys`	A sequence of keys. TYPE: `Sequence[K]`

RETURNS	DESCRIPTION
`list[V \| None]`	A sequence of optional values associated with the keys.
`list[V \| None]`	If a key is not found, the corresponding value will be `None`.

amget `async` ¶

amget(keys: Sequence[K]) -> list[V | None]

Async get the values associated with the given keys.

PARAMETER	DESCRIPTION
`keys`	A sequence of keys. TYPE: `Sequence[K]`

RETURNS	DESCRIPTION
`list[V \| None]`	A sequence of optional values associated with the keys.
`list[V \| None]`	If a key is not found, the corresponding value will be `None`.

mset ¶

mset(key_value_pairs: Sequence[tuple[K, V]]) -> None

Set the values for the given keys.

PARAMETER	DESCRIPTION
`key_value_pairs`	A sequence of key-value pairs. TYPE: `Sequence[tuple[K, V]]`

amset `async` ¶

amset(key_value_pairs: Sequence[tuple[K, V]]) -> None

Async set the values for the given keys.

PARAMETER	DESCRIPTION
`key_value_pairs`	A sequence of key-value pairs. TYPE: `Sequence[tuple[K, V]]`

mdelete ¶

mdelete(keys: Sequence[K]) -> None

Delete the given keys and their associated values.

PARAMETER	DESCRIPTION
`keys`	A sequence of keys to delete. TYPE: `Sequence[K]`

amdelete `async` ¶

amdelete(keys: Sequence[K]) -> None

Async delete the given keys and their associated values.

PARAMETER	DESCRIPTION
`keys`	A sequence of keys to delete. TYPE: `Sequence[K]`

yield_keys ¶

yield_keys(*, prefix: str | None = None) -> Iterator[K] | Iterator[str]

Get an iterator over keys that match the given prefix.

PARAMETER	DESCRIPTION
`prefix`	The prefix to match. TYPE: `str \| None` DEFAULT: `None`

YIELDS	DESCRIPTION
`Iterator[K] \| Iterator[str]`	Keys that match the given prefix.

ayield_keys `async` ¶

ayield_keys(*, prefix: str | None = None) -> AsyncIterator[K] | AsyncIterator[str]

Async get an iterator over keys that match the given prefix.

PARAMETER	DESCRIPTION
`prefix`	The prefix to match. TYPE: `str \| None` DEFAULT: `None`

YIELDS	DESCRIPTION
`AsyncIterator[K] \| AsyncIterator[str]`	Keys that match the given prefix.

LocalFileStore ¶

Bases: ByteStore

BaseStore interface that works on the local file system.

Examples:

Create a LocalFileStore instance and perform operations on it:

from langchain_classic.storage import LocalFileStore

# Instantiate the LocalFileStore with the root path
file_store = LocalFileStore("/path/to/root")

# Set values for keys
file_store.mset([("key1", b"value1"), ("key2", b"value2")])

# Get values for keys
values = file_store.mget(["key1", "key2"])  # Returns [b"value1", b"value2"]

# Delete keys
file_store.mdelete(["key1"])

# Iterate over keys
for key in file_store.yield_keys():
    print(key)  # noqa: T201

METHOD	DESCRIPTION
`__init__`	Implement the `BaseStore` interface for the local file system.
`mget`	Get the values associated with the given keys.
`mset`	Set the values for the given keys.
`mdelete`	Delete the given keys and their associated values.
`yield_keys`	Get an iterator over keys that match the given prefix.

init ¶

__init__(
    root_path: str | Path,
    *,
    chmod_file: int | None = None,
    chmod_dir: int | None = None,
    update_atime: bool = False,
) -> None

Implement the BaseStore interface for the local file system.

PARAMETER	DESCRIPTION
`root_path`	The root path of the file store. All keys are interpreted as paths relative to this root. TYPE: `str \| Path`
`chmod_file`	Sets permissions for newly created files, overriding the current `umask` if needed. TYPE: `int \| None` DEFAULT: `None`
`chmod_dir`	Sets permissions for newly created dirs, overriding the current `umask` if needed. TYPE: `int \| None` DEFAULT: `None`
`update_atime`	Updates the filesystem access time (but not the modified time) when a file is read. This allows MRU/LRU cache policies to be implemented for filesystems where access time updates are disabled. TYPE: `bool` DEFAULT: `False`

mget ¶

mget(keys: Sequence[str]) -> list[bytes | None]

Get the values associated with the given keys.

PARAMETER	DESCRIPTION
`keys`	A sequence of keys. TYPE: `Sequence[str]`

RETURNS	DESCRIPTION
`list[bytes \| None]`	A sequence of optional values associated with the keys.
`list[bytes \| None]`	If a key is not found, the corresponding value will be `None`.

mset ¶

mset(key_value_pairs: Sequence[tuple[str, bytes]]) -> None

Set the values for the given keys.

PARAMETER	DESCRIPTION
`key_value_pairs`	A sequence of key-value pairs. TYPE: `Sequence[tuple[str, bytes]]`

mdelete ¶

mdelete(keys: Sequence[str]) -> None

Delete the given keys and their associated values.

PARAMETER	DESCRIPTION
`keys`	A sequence of keys to delete. TYPE: `Sequence[str]`

yield_keys ¶

yield_keys(prefix: str | None = None) -> Iterator[str]

Get an iterator over keys that match the given prefix.

PARAMETER	DESCRIPTION
`prefix`	The prefix to match. TYPE: `str \| None` DEFAULT: `None`

YIELDS	DESCRIPTION
`str`	Keys that match the given prefix.

Storage¶

langchain_classic.storage ¶

EncoderBackedStore ¶

__init__ ¶

mget ¶

amget async ¶

mset ¶

amset async ¶

mdelete ¶

amdelete async ¶

yield_keys ¶

ayield_keys async ¶

LocalFileStore ¶

__init__ ¶

mget ¶

mset ¶

mdelete ¶

yield_keys ¶

init ¶

amget `async` ¶

amset `async` ¶

amdelete `async` ¶

ayield_keys `async` ¶

init ¶