Access PI Point from AF Attribute

[Hugovdberg]

From an email I received recently:

We are currently using your python library to get access to PI AF info. Our interest is on extracting the PI points within a PI AF element, and we have been able to, but then, from those PI points, getting the description attribute related to each PI DA tag. We know how to do that from PI Datalink though for automation, the best thing would be to reach description attribute from python directly. We would appreciate if you could provide support on this topic.

[Hugovdberg]

This is linked to issue #528. Currently it isn't implemented in PIconnect yet, so in the meantime it is probably best to use something like this:

import PIconnect as PI

with PI.PIAFDatabase() as db:
    elem = db.descendant(r"Some\Path\To\An\Element")
    attr = elem.attributes["Interesting attribute"]
    # Here it gets a little dirty:
    data_ref =attr.attribute.DataReference # returns the data reference for the underlying .NET AFAttribute
    if data_ref.Name == "PI Point":
        pi_point = PI.PI.PIPoint(data_ref.PIPoint) # construct a python PIPoint object from the returned .NET object
        print(pi_point.description)

[Hugovdberg]

An update on this: since PIconnect version 0.10.4 the Attribute objects have a new property called data_reference that can be used to access the underlying PIPoint object:

import PIconnect as PI

with PI.PIAFDatabase() as db:
    elem = db.descendant(r"Some\Path\To\An\Element")
    attr = elem.attributes["Interesting attribute"]
    pipoint = attr.data_reference.pi_point
    if pipoint is not None:
        print(pi_point.description)

The attribute pi_point is only not None if the data reference is actually associated with a PI Point.