Channels¶

Classes:

Name	Description
`BaseChannel`	Base class for all channels.

BaseChannel ¶

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

Base class for all channels.

Methods:

Name	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.

Attributes:

Name	Type	Description
`ValueType`	`Any`	The type of the value stored in the channel.
`UpdateType`	`Any`	The type of the update received by the channel.

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() -> C

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: C) -> 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.

Classes:

Name	Description
`Topic`	A configurable PubSub Topic.
`LastValue`	Stores the last value received, can receive at most one value per step.
`EphemeralValue`	Stores the value received in the step immediately preceding, clears after.
`BinaryOperatorAggregate`	Stores the result of applying a binary operator to the current value and each new value.
`AnyValue`	Stores the last value received, assumes that if multiple values are

Topic ¶

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

A configurable PubSub Topic.

Parameters:

Name	Type	Description	Default
`typ`	`type[Value]`	The type of the value stored in the channel.	required
`accumulate`	`bool`	Whether to accumulate values across steps. If False, the channel will be emptied after each step.	`False`

Methods:

Name	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.

Attributes:

Name	Type	Description
`ValueType`	`Any`	The type of the value stored in the channel.
`UpdateType`	`Any`	The type of the update received by the channel.

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.

LastValue ¶

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

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

Methods:

Name	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.

Attributes:

Name	Type	Description
`ValueType`	`type[Value]`	The type of the value stored in the channel.
`UpdateType`	`type[Value]`	The type of the update received by the channel.

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.

EphemeralValue ¶

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

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

Methods:

Name	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.

Attributes:

Name	Type	Description
`ValueType`	`type[Value]`	The type of the value stored in the channel.
`UpdateType`	`type[Value]`	The type of the update received by the channel.

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.

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)

Methods:

Name	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.

Attributes:

Name	Type	Description
`ValueType`	`type[Value]`	The type of the value stored in the channel.
`UpdateType`	`type[Value]`	The type of the update received by the channel.

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.

AnyValue ¶

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

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

Methods:

Name	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.

Attributes:

Name	Type	Description
`ValueType`	`type[Value]`	The type of the value stored in the channel.
`UpdateType`	`type[Value]`	The type of the update received by the channel.

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.

Channels¶

BaseChannel ¶

ValueType abstractmethod property ¶

UpdateType abstractmethod property ¶

copy ¶

checkpoint ¶

from_checkpoint abstractmethod ¶

get abstractmethod ¶

is_available ¶

update abstractmethod ¶

consume ¶

finish ¶

Topic ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

LastValue ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

EphemeralValue ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

BinaryOperatorAggregate ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

AnyValue ¶

ValueType property ¶

UpdateType property ¶

consume ¶

finish ¶

copy ¶

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` ¶