Links

Link

class crappy.links.Link(*args, **kwargs)

This class is used for transferring information between two instances of Block.

The created Link is unidirectional, from the input Block to the output Block. Under the hood, a Link is basically a multiprocessing.Pipe with extra features.

Note

It is possible to add one or multiple Modifier to modify the transferred value. The Modifiers should be callables taking a dict as argument and returning a dict. They can be functions, or preferably children of Modifier.

Added in version 1.4.0.

__init__(input_block, output_block, modifiers: List[Callable[[Dict[str, Any]], Dict[str, Any]]] | None = None, name: str | None = None) → None

Sets the instance attributes.

Parameters:

• input_block – The Block sending data through the Link.

• output_block – The Block receiving data through the Link.

• modifiers – A list containing callables. If several objects given, they will be called in the given order. Refer to Modifier for more information.

• name – Name of the Link, to differentiate it from the others when debugging. If no specific name is given, the Links are numbered in the order in which they are instantiated in the script.

Changed in version 1.5.9: renamed condition argument to conditions

Changed in version 1.5.9: renamed modifier argument to modifiers

Removed in version 2.0.0: conditions, timeout and action arguments

log(log_level: int, msg: str) → None

Method for recording log messages from the Link.

Parameters:

• log_level – An int indicating the logging level of the message.

• msg – The message to log, as a str.

Added in version 2.0.0.

poll() → bool

Returns True if there’s data available for reading.

Added in version 2.0.0.

send(value: Dict[str, Any]) → None

Sends a value from the upstream Block to the downstream Block.

Before sending, applies the given Modifiers and makes sure there’s room in the Pipe for sending the data (Linux only).

recv() → Dict[str, Any]

Reads a single value from the Link and returns it.

The read value is the oldest available in the Link, see recv_last() for reading the newest available value.

If no data is available in the Link, returns an empty dict.

Returns:

A dict whose keys are the labels being sent, and for each key a single value (usually a float or a str).

Removed in version 2.0.0: blocking argument

recv_last() → Dict[str, Any]

Reads all the available values in the Link, and returns the newest one.

If no data is available in the Link, returns an empty dict. All the data that is not returned is permanently dropped.

Returns:

A dict whose keys are the labels being sent, and for each key a single value (usually a float or a str).

Removed in version 2.0.0: blocking argument

recv_chunk() → Dict[str, List[Any]]

Reads all the available values in the Link, and returns them all.

Returns:

A dict whose keys are the labels being sent, and for each key a list of the received values. The first item in the list is the oldest one available in the Link, the last item is the newest available.

Removed in version 1.5.9: length argument

Added in version 1.5.9: blocking argument

Removed in version 2.0.0: blocking argument