initial commit

venv/Lib/site-packages/langgraph/channels/ephemeral_value.py

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