initial commit

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

@@ -0,0 +1,151 @@
+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,
+    ErrorCode,
+    InvalidUpdateError,
+    create_error_message,
+)
+
+__all__ = ("LastValue", "LastValueAfterFinish")
+
+
+class LastValue(Generic[Value], BaseChannel[Value, Value, Value]):
+    """Stores the last value received, can receive at most one value per step."""
+
+    __slots__ = ("value",)
+
+    value: Value | Any
+
+    def __init__(self, typ: Any, key: str = "") -> None:
+        super().__init__(typ, key)
+        self.value = MISSING
+
+    def __eq__(self, value: object) -> bool:
+        return isinstance(value, LastValue)
+
+    @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.key)
+        empty.value = self.value
+        return empty
+
+    def from_checkpoint(self, checkpoint: Value) -> Self:
+        empty = self.__class__(self.typ, self.key)
+        if checkpoint is not MISSING:
+            empty.value = checkpoint
+        return empty
+
+    def update(self, values: Sequence[Value]) -> bool:
+        if len(values) == 0:
+            return False
+        if len(values) != 1:
+            msg = create_error_message(
+                message=f"At key '{self.key}': Can receive only one value per step. Use an Annotated key to handle multiple values.",
+                error_code=ErrorCode.INVALID_CONCURRENT_GRAPH_UPDATE,
+            )
+            raise InvalidUpdateError(msg)
+
+        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
+
+
+class LastValueAfterFinish(
+    Generic[Value], BaseChannel[Value, Value, tuple[Value, bool]]
+):
+    """Stores the last value received, but only made available after finish().
+    Once made available, clears the value."""
+
+    __slots__ = ("value", "finished")
+
+    value: Value | Any
+    finished: bool
+
+    def __init__(self, typ: Any, key: str = "") -> None:
+        super().__init__(typ, key)
+        self.value = MISSING
+        self.finished = False
+
+    def __eq__(self, value: object) -> bool:
+        return isinstance(value, LastValueAfterFinish)
+
+    @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 checkpoint(self) -> tuple[Value | Any, bool] | Any:
+        if self.value is MISSING:
+            return MISSING
+        return (self.value, self.finished)
+
+    def from_checkpoint(self, checkpoint: tuple[Value | Any, bool] | Any) -> Self:
+        empty = self.__class__(self.typ)
+        empty.key = self.key
+        if checkpoint is not MISSING:
+            empty.value, empty.finished = checkpoint
+        return empty
+
+    def update(self, values: Sequence[Value | Any]) -> bool:
+        if len(values) == 0:
+            return False
+
+        self.finished = False
+        self.value = values[-1]
+        return True
+
+    def consume(self) -> bool:
+        if self.finished:
+            self.finished = False
+            self.value = MISSING
+            return True
+
+        return False
+
+    def finish(self) -> bool:
+        if not self.finished and self.value is not MISSING:
+            self.finished = True
+            return True
+        else:
+            return False
+
+    def get(self) -> Value:
+        if self.value is MISSING or not self.finished:
+            raise EmptyChannelError()
+        return self.value
+
+    def is_available(self) -> bool:
+        return self.value is not MISSING and self.finished