meshed.components#

Ready-made extraction components for meshed graphs.

A DAG node needs a __name__ and a signature to know what var node it reads and what var node it writes. Plain operator.itemgetter and attrgetter objects have no __name__ and no usable one-parameter signature, so this module wraps them in Extractor, a callable that carries a chosen name and a single positional-only parameter, and can therefore be listed directly among the functions given to DAG.

Main entry points:

  • Itemgetter: extracts one item, or a tuple of items, from its input by key.

  • AttrGetter: extracts one attribute, or a tuple of attributes, from its input.

  • Extractor: the general form; give it a factory and the parameters to build with.

>>> from meshed.components import Itemgetter
>>> get_ab = Itemgetter(['a', 'b'])
>>> get_ab({'a': 1, 'b': 2, 'c': 3})
(1, 2)

Classes

Extractor(extractor_factory, extractor_params, *)

Callable extracting from its single input, named and signed to be a DAG node.
class meshed.components.Extractor(extractor_factory, extractor_params, *, name='extractor', input_name='x')[source]#

Bases: object

Callable extracting from its single input, named and signed to be a DAG node.

Calling an instance applies extractor_factory(extractor_params) to the input. The instance carries a chosen __name__ and a one-parameter signature, which is what DAG needs to wire it to var nodes.

Parameters:

  • extractor_factory (Callable[[Any], Callable]) – Called once with extractor_params to make the function that is applied to the input.

  • extractor_params (Any) – Passed to extractor_factory.

  • name (str) – Becomes the __name__ of the instance.

  • input_name (str) – Name of the single positional-only parameter of the instance’s signature (the var node a DAG will bind it to).