mirror of
https://github.com/langchain-ai/langgraph.git
synced 2026-09-30 13:35:09 +02:00
116 lines
3.6 KiB
Python
116 lines
3.6 KiB
Python
from abc import ABC, abstractmethod
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from contextlib import asynccontextmanager, contextmanager
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from typing import (
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Any,
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AsyncGenerator,
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Generator,
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Generic,
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Mapping,
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Optional,
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Sequence,
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TypeVar,
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)
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from typing_extensions import Self
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Value = TypeVar("Value")
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Update = TypeVar("Update")
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Checkpoint = TypeVar("Checkpoint")
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class EmptyChannelError(Exception):
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"""Raised when attempting to get the value of a channel that hasn't been updated
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for the first time yet."""
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pass
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class InvalidUpdateError(Exception):
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"""Raised when attempting to update a channel with an invalid sequence of updates."""
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pass
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class BaseChannel(Generic[Value, Update, Checkpoint], ABC):
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@property
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@abstractmethod
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def ValueType(self) -> Any:
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"""The type of the value stored in the channel."""
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@property
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@abstractmethod
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def UpdateType(self) -> Any:
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"""The type of the update received by the channel."""
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@contextmanager
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@abstractmethod
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def empty(
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self, checkpoint: Optional[Checkpoint] = None
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) -> Generator[Self, None, None]:
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"""Return a new identical channel, optionally initialized from a checkpoint."""
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@asynccontextmanager
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async def aempty(
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self, checkpoint: Optional[str] = None
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) -> AsyncGenerator[Self, None]:
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"""Return a new identical channel, optionally initialized from a checkpoint."""
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with self.empty(checkpoint) as value:
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yield value
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@abstractmethod
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def update(self, values: Sequence[Update]) -> None:
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"""Update the channel's value with the given sequence of updates.
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The order of the updates in the sequence is arbitrary.
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Raises InvalidUpdateError if the sequence of updates is invalid."""
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@abstractmethod
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def get(self) -> Value:
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"""Return the current value of the channel.
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Raises EmptyChannelError if the channel is empty (never updated yet)."""
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@abstractmethod
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def checkpoint(self) -> Checkpoint | None:
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"""Return a string representation of the channel's current state,
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or None if the channel doesn't support checkpoints.
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Raises EmptyChannelError if the channel is empty (never updated yet)."""
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@contextmanager
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def ChannelsManager(
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channels: Mapping[str, BaseChannel],
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checkpoint: Optional[Mapping[str, Any]],
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) -> Generator[Mapping[str, BaseChannel], None, None]:
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"""Manage channels for the lifetime of a Pregel invocation (multiple steps)."""
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# TODO use https://docs.python.org/3/library/contextlib.html#contextlib.ExitStack
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checkpoint = checkpoint or {}
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empty = {k: v.empty(checkpoint.get(k)) for k, v in channels.items()}
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try:
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yield {k: v.__enter__() for k, v in empty.items()}
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finally:
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for v in empty.values():
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v.__exit__(None, None, None)
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@asynccontextmanager
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async def AsyncChannelsManager(
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channels: Mapping[str, BaseChannel],
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checkpoint: Optional[Mapping[str, Any]],
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) -> AsyncGenerator[Mapping[str, BaseChannel], None]:
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"""Manage channels for the lifetime of a Pregel invocation (multiple steps)."""
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checkpoint = checkpoint or {}
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empty = {k: v.aempty(checkpoint.get(k)) for k, v in channels.items()}
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try:
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yield {k: await v.__aenter__() for k, v in empty.items()}
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finally:
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for v in empty.values():
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await v.__aexit__(None, None, None)
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def create_checkpoint(channels: Mapping[str, BaseChannel]) -> Mapping[str, Any]:
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"""Create a checkpoint for the given channels."""
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checkpoint = {k: v.checkpoint() for k, v in channels.items()}
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return {k: v for k, v in checkpoint.items() if v is not None}
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