Channels

langgraph.channels.base ¶

BaseChannel ¶

Bases: Generic[Value, Update, Checkpoint], ABC

Base class for all channels.

METHOD	DESCRIPTION
`copy`	Return a copy of the channel.
`checkpoint`	Return a serializable representation of the channel's current state.
`from_checkpoint`	Return a new identical channel, optionally initialized from a checkpoint.
`get`	Return the current value of the channel.
`is_available`	Return `True` if the channel is available (not empty), `False` otherwise.
`update`	Update the channel's value with the given sequence of updates.
`consume`	Notify the channel that a subscribed task ran. By default, no-op.
`finish`	Notify the channel that the Pregel run is finishing. By default, no-op.

ValueType `abstractmethod` `property` ¶

ValueType: Any

The type of the value stored in the channel.

UpdateType `abstractmethod` `property` ¶

UpdateType: Any

The type of the update received by the channel.

copy ¶

copy() -> Self

Return a copy of the channel. By default, delegates to checkpoint() and from_checkpoint(). Subclasses can override this method with a more efficient implementation.

checkpoint ¶

checkpoint() -> Checkpoint | Any

Return a serializable representation of the channel's current state. Raises EmptyChannelError if the channel is empty (never updated yet), or doesn't support checkpoints.

from_checkpoint `abstractmethod` ¶

from_checkpoint(checkpoint: Checkpoint | Any) -> Self

Return a new identical channel, optionally initialized from a checkpoint. If the checkpoint contains complex data structures, they should be copied.

get `abstractmethod` ¶

get() -> Value

Return the current value of the channel.

Raises EmptyChannelError if the channel is empty (never updated yet).

is_available ¶

is_available() -> bool

Return True if the channel is available (not empty), False otherwise. Subclasses should override this method to provide a more efficient implementation than calling get() and catching EmptyChannelError.

update `abstractmethod` ¶

update(values: Sequence[Update]) -> bool

Update the channel's value with the given sequence of updates. The order of the updates in the sequence is arbitrary. This method is called by Pregel for all channels at the end of each step. If there are no updates, it is called with an empty sequence. Raises InvalidUpdateError if the sequence of updates is invalid. Returns True if the channel was updated, False otherwise.

consume ¶

consume() -> bool

Notify the channel that a subscribed task ran. By default, no-op. A channel can use this method to modify its state, preventing the value from being consumed again.

Returns True if the channel was updated, False otherwise.

finish ¶

finish() -> bool

Notify the channel that the Pregel run is finishing. By default, no-op. A channel can use this method to modify its state, preventing finish.

Returns True if the channel was updated, False otherwise.

langgraph.channels ¶

Topic ¶

Bases: Generic[Value], BaseChannel[Sequence[Value], Value | list[Value], list[Value]]

A configurable PubSub Topic.

PARAMETER	DESCRIPTION
`typ`	The type of the value stored in the channel. TYPE: `type[Value]`
`accumulate`	Whether to accumulate values across steps. If `False`, the channel will be emptied after each step. TYPE: `bool` DEFAULT: `False`

METHOD	DESCRIPTION
`consume`	Notify the channel that a subscribed task ran. By default, no-op.
`finish`	Notify the channel that the Pregel run is finishing. By default, no-op.
`copy`	Return a copy of the channel.
`checkpoint`	Return a serializable representation of the channel's current state.
`from_checkpoint`	Return a new identical channel, optionally initialized from a checkpoint.
`update`	Update the channel's value with the given sequence of updates.
`get`	Return the current value of the channel.
`is_available`	Return `True` if the channel is available (not empty), `False` otherwise.

ValueType `property` ¶

ValueType: Any

The type of the value stored in the channel.

UpdateType `property` ¶

UpdateType: Any

The type of the update received by the channel.

consume ¶

consume() -> bool

Notify the channel that a subscribed task ran. By default, no-op. A channel can use this method to modify its state, preventing the value from being consumed again.

Returns True if the channel was updated, False otherwise.

finish ¶

finish() -> bool

Notify the channel that the Pregel run is finishing. By default, no-op. A channel can use this method to modify its state, preventing finish.

Returns True if the channel was updated, False otherwise.

copy ¶

copy() -> Self

Return a copy of the channel.

checkpoint ¶

checkpoint() -> list[Value]

Return a serializable representation of the channel's current state. Raises EmptyChannelError if the channel is empty (never updated yet), or doesn't support checkpoints.

from_checkpoint ¶

from_checkpoint(checkpoint: list[Value]) -> Self

Return a new identical channel, optionally initialized from a checkpoint. If the checkpoint contains complex data structures, they should be copied.

update ¶

update(values: Sequence[Value | list[Value]]) -> bool

Update the channel's value with the given sequence of updates. The order of the updates in the sequence is arbitrary. This method is called by Pregel for all channels at the end of each step. If there are no updates, it is called with an empty sequence. Raises InvalidUpdateError if the sequence of updates is invalid. Returns True if the channel was updated, False otherwise.

get ¶

get() -> Sequence[Value]

Return the current value of the channel.

Raises EmptyChannelError if the channel is empty (never updated yet).

is_available ¶

is_available() -> bool

Return True if the channel is available (not empty), False otherwise. Subclasses should override this method to provide a more efficient implementation than calling get() and catching EmptyChannelError.

LastValue ¶

Bases: Generic[Value], BaseChannel[Value, Value, Value]

Stores the last value received, can receive at most one value per step.

METHOD	DESCRIPTION
`consume`	Notify the channel that a subscribed task ran. By default, no-op.
`finish`	Notify the channel that the Pregel run is finishing. By default, no-op.
`copy`	Return a copy of the channel.
`from_checkpoint`	Return a new identical channel, optionally initialized from a checkpoint.
`update`	Update the channel's value with the given sequence of updates.
`get`	Return the current value of the channel.
`is_available`	Return `True` if the channel is available (not empty), `False` otherwise.
`checkpoint`	Return a serializable representation of the channel's current state.

ValueType `property` ¶

ValueType: type[Value]

The type of the value stored in the channel.

UpdateType `property` ¶

UpdateType: type[Value]

The type of the update received by the channel.

consume ¶

consume() -> bool

Notify the channel that a subscribed task ran. By default, no-op. A channel can use this method to modify its state, preventing the value from being consumed again.

Returns True if the channel was updated, False otherwise.

finish ¶

finish() -> bool

Notify the channel that the Pregel run is finishing. By default, no-op. A channel can use this method to modify its state, preventing finish.

Returns True if the channel was updated, False otherwise.

copy ¶

copy() -> Self

Return a copy of the channel.

from_checkpoint ¶

from_checkpoint(checkpoint: Value) -> Self

Return a new identical channel, optionally initialized from a checkpoint. If the checkpoint contains complex data structures, they should be copied.

update ¶

update(values: Sequence[Value]) -> bool

Update the channel's value with the given sequence of updates. The order of the updates in the sequence is arbitrary. This method is called by Pregel for all channels at the end of each step. If there are no updates, it is called with an empty sequence. Raises InvalidUpdateError if the sequence of updates is invalid. Returns True if the channel was updated, False otherwise.

get ¶

get() -> Value

Return the current value of the channel.

Raises EmptyChannelError if the channel is empty (never updated yet).

is_available ¶

is_available() -> bool

Return True if the channel is available (not empty), False otherwise. Subclasses should override this method to provide a more efficient implementation than calling get() and catching EmptyChannelError.

checkpoint ¶

checkpoint() -> Value

Return a serializable representation of the channel's current state. Raises EmptyChannelError if the channel is empty (never updated yet), or doesn't support checkpoints.

EphemeralValue ¶

Bases: Generic[Value], BaseChannel[Value, Value, Value]

Stores the value received in the step immediately preceding, clears after.

METHOD	DESCRIPTION
`consume`	Notify the channel that a subscribed task ran. By default, no-op.
`finish`	Notify the channel that the Pregel run is finishing. By default, no-op.
`copy`	Return a copy of the channel.
`from_checkpoint`	Return a new identical channel, optionally initialized from a checkpoint.
`update`	Update the channel's value with the given sequence of updates.
`get`	Return the current value of the channel.
`is_available`	Return `True` if the channel is available (not empty), `False` otherwise.
`checkpoint`	Return a serializable representation of the channel's current state.

ValueType `property` ¶

ValueType: type[Value]

The type of the value stored in the channel.

UpdateType `property` ¶

UpdateType: type[Value]

The type of the update received by the channel.

consume ¶

consume() -> bool

Notify the channel that a subscribed task ran. By default, no-op. A channel can use this method to modify its state, preventing the value from being consumed again.

Returns True if the channel was updated, False otherwise.

finish ¶

finish() -> bool

Notify the channel that the Pregel run is finishing. By default, no-op. A channel can use this method to modify its state, preventing finish.

Returns True if the channel was updated, False otherwise.

copy ¶

copy() -> Self

Return a copy of the channel.

from_checkpoint ¶

from_checkpoint(checkpoint: Value) -> Self

Return a new identical channel, optionally initialized from a checkpoint. If the checkpoint contains complex data structures, they should be copied.

update ¶

update(values: Sequence[Value]) -> bool

Update the channel's value with the given sequence of updates. The order of the updates in the sequence is arbitrary. This method is called by Pregel for all channels at the end of each step. If there are no updates, it is called with an empty sequence. Raises InvalidUpdateError if the sequence of updates is invalid. Returns True if the channel was updated, False otherwise.

get ¶

get() -> Value

Return the current value of the channel.

Raises EmptyChannelError if the channel is empty (never updated yet).

is_available ¶

is_available() -> bool

Return True if the channel is available (not empty), False otherwise. Subclasses should override this method to provide a more efficient implementation than calling get() and catching EmptyChannelError.

checkpoint ¶

checkpoint() -> Value

Return a serializable representation of the channel's current state. Raises EmptyChannelError if the channel is empty (never updated yet), or doesn't support checkpoints.

BinaryOperatorAggregate ¶

Bases: Generic[Value], BaseChannel[Value, Value, Value]

Stores the result of applying a binary operator to the current value and each new value.

import operator

total = Channels.BinaryOperatorAggregate(int, operator.add)

METHOD	DESCRIPTION
`consume`	Notify the channel that a subscribed task ran. By default, no-op.
`finish`	Notify the channel that the Pregel run is finishing. By default, no-op.
`copy`	Return a copy of the channel.
`from_checkpoint`	Return a new identical channel, optionally initialized from a checkpoint.
`update`	Update the channel's value with the given sequence of updates.
`get`	Return the current value of the channel.
`is_available`	Return `True` if the channel is available (not empty), `False` otherwise.
`checkpoint`	Return a serializable representation of the channel's current state.

ValueType `property` ¶

ValueType: type[Value]

The type of the value stored in the channel.

UpdateType `property` ¶

UpdateType: type[Value]

The type of the update received by the channel.

consume ¶

consume() -> bool

Notify the channel that a subscribed task ran. By default, no-op. A channel can use this method to modify its state, preventing the value from being consumed again.

Returns True if the channel was updated, False otherwise.

finish ¶

finish() -> bool

Notify the channel that the Pregel run is finishing. By default, no-op. A channel can use this method to modify its state, preventing finish.

Returns True if the channel was updated, False otherwise.

copy ¶

copy() -> Self

Return a copy of the channel.

from_checkpoint ¶

from_checkpoint(checkpoint: Value) -> Self

Return a new identical channel, optionally initialized from a checkpoint. If the checkpoint contains complex data structures, they should be copied.

update ¶

update(values: Sequence[Value]) -> bool

Update the channel's value with the given sequence of updates. The order of the updates in the sequence is arbitrary. This method is called by Pregel for all channels at the end of each step. If there are no updates, it is called with an empty sequence. Raises InvalidUpdateError if the sequence of updates is invalid. Returns True if the channel was updated, False otherwise.

get ¶

get() -> Value

Return the current value of the channel.

Raises EmptyChannelError if the channel is empty (never updated yet).

is_available ¶

is_available() -> bool

Return True if the channel is available (not empty), False otherwise. Subclasses should override this method to provide a more efficient implementation than calling get() and catching EmptyChannelError.

checkpoint ¶

checkpoint() -> Value

Return a serializable representation of the channel's current state. Raises EmptyChannelError if the channel is empty (never updated yet), or doesn't support checkpoints.

AnyValue ¶

Bases: Generic[Value], BaseChannel[Value, Value, Value]

Stores the last value received, assumes that if multiple values are received, they are all equal.

METHOD	DESCRIPTION
`consume`	Notify the channel that a subscribed task ran. By default, no-op.
`finish`	Notify the channel that the Pregel run is finishing. By default, no-op.
`copy`	Return a copy of the channel.
`from_checkpoint`	Return a new identical channel, optionally initialized from a checkpoint.
`update`	Update the channel's value with the given sequence of updates.
`get`	Return the current value of the channel.
`is_available`	Return `True` if the channel is available (not empty), `False` otherwise.
`checkpoint`	Return a serializable representation of the channel's current state.

ValueType `property` ¶

ValueType: type[Value]

The type of the value stored in the channel.

UpdateType `property` ¶

UpdateType: type[Value]

The type of the update received by the channel.

consume ¶

consume() -> bool

Notify the channel that a subscribed task ran. By default, no-op. A channel can use this method to modify its state, preventing the value from being consumed again.

Returns True if the channel was updated, False otherwise.

finish ¶

finish() -> bool

Notify the channel that the Pregel run is finishing. By default, no-op. A channel can use this method to modify its state, preventing finish.

Returns True if the channel was updated, False otherwise.

copy ¶

copy() -> Self

Return a copy of the channel.

from_checkpoint ¶

from_checkpoint(checkpoint: Value) -> Self

Return a new identical channel, optionally initialized from a checkpoint. If the checkpoint contains complex data structures, they should be copied.

update ¶

update(values: Sequence[Value]) -> bool

Update the channel's value with the given sequence of updates. The order of the updates in the sequence is arbitrary. This method is called by Pregel for all channels at the end of each step. If there are no updates, it is called with an empty sequence. Raises InvalidUpdateError if the sequence of updates is invalid. Returns True if the channel was updated, False otherwise.

get ¶

get() -> Value

Return the current value of the channel.

Raises EmptyChannelError if the channel is empty (never updated yet).

is_available ¶

is_available() -> bool

Return True if the channel is available (not empty), False otherwise. Subclasses should override this method to provide a more efficient implementation than calling get() and catching EmptyChannelError.

checkpoint ¶

checkpoint() -> Value

Return a serializable representation of the channel's current state. Raises EmptyChannelError if the channel is empty (never updated yet), or doesn't support checkpoints.

Channels

langgraph.channels.base ¶

BaseChannel ¶

ValueType abstractmethod property ¶

UpdateType abstractmethod property ¶

copy ¶

checkpoint ¶

from_checkpoint abstractmethod ¶

get abstractmethod ¶

is_available ¶

update abstractmethod ¶

consume ¶

finish ¶

langgraph.channels ¶

Topic ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

checkpoint ¶

from_checkpoint ¶

update ¶

get ¶

is_available ¶

LastValue ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

from_checkpoint ¶

update ¶

get ¶

is_available ¶

checkpoint ¶

EphemeralValue ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

from_checkpoint ¶

update ¶

get ¶

is_available ¶

checkpoint ¶

BinaryOperatorAggregate ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

from_checkpoint ¶

update ¶

get ¶

is_available ¶

checkpoint ¶

AnyValue ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

from_checkpoint ¶

update ¶

get ¶

is_available ¶

checkpoint ¶

ValueType `abstractmethod` `property` ¶

UpdateType `abstractmethod` `property` ¶

from_checkpoint `abstractmethod` ¶

get `abstractmethod` ¶

update `abstractmethod` ¶

ValueType `property` ¶

UpdateType `property` ¶

ValueType `property` ¶

UpdateType `property` ¶

ValueType `property` ¶

UpdateType `property` ¶

ValueType `property` ¶

UpdateType `property` ¶

ValueType `property` ¶

UpdateType `property` ¶