80 lines
2.3 KiB
Python
80 lines
2.3 KiB
Python
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from __future__ import annotations
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from collections.abc import Sequence
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from typing import Any, Generic
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from typing_extensions import Self
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from langgraph._internal._typing import MISSING
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from langgraph.channels.base import BaseChannel, Value
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from langgraph.errors import EmptyChannelError, InvalidUpdateError
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__all__ = ("EphemeralValue",)
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class EphemeralValue(Generic[Value], BaseChannel[Value, Value, Value]):
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"""Stores the value received in the step immediately preceding, clears after."""
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__slots__ = ("value", "guard")
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value: Value | Any
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guard: bool
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def __init__(self, typ: Any, guard: bool = True) -> None:
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super().__init__(typ)
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self.guard = guard
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self.value = MISSING
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def __eq__(self, value: object) -> bool:
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return isinstance(value, EphemeralValue) and value.guard == self.guard
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@property
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def ValueType(self) -> type[Value]:
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"""The type of the value stored in the channel."""
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return self.typ
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@property
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def UpdateType(self) -> type[Value]:
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"""The type of the update received by the channel."""
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return self.typ
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def copy(self) -> Self:
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"""Return a copy of the channel."""
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empty = self.__class__(self.typ, self.guard)
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empty.key = self.key
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empty.value = self.value
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return empty
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def from_checkpoint(self, checkpoint: Value) -> Self:
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empty = self.__class__(self.typ, self.guard)
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empty.key = self.key
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if checkpoint is not MISSING:
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empty.value = checkpoint
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return empty
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def update(self, values: Sequence[Value]) -> bool:
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if len(values) == 0:
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if self.value is not MISSING:
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self.value = MISSING
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return True
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else:
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return False
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if len(values) != 1 and self.guard:
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raise InvalidUpdateError(
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f"At key '{self.key}': EphemeralValue(guard=True) can receive only one value per step. Use guard=False if you want to store any one of multiple values."
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)
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self.value = values[-1]
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return True
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def get(self) -> Value:
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if self.value is MISSING:
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raise EmptyChannelError()
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return self.value
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def is_available(self) -> bool:
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return self.value is not MISSING
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def checkpoint(self) -> Value:
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return self.value
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