GPIBInstrument.wait_for_srq() raises NotImplementedError

pyvisa.resources.gpib.GPIBInstrument.wait_for_srq() calls enable_event(), wait_on_event(), and discard_events() of the underlying visalib. However, PyVisaLibrary does not implement those methods so NotImplementedError is raised.

One way to go about this is to delegate the missing methods to underlying pyvisa-py session objects and implement event support there.

Another possibility is to notice that wait_for_srq() is quite universal - in particular, VISA Service Request events should be supported by GPIB INSTR, GPIB INTFC, GPIB-VXI INSTR, TCPIP INSTR, USB INSTR, and VXI INSTR. So, wait_for_srq() could be moved to pyvisa.highlevel.VisaLibraryBase. This would make it easier to implement an overload in PyVisaLibrary before full-blown event support in pyvisa-py is ready.

[MatthieuDartiailh]

Could you open a [WIP] PR to make the changes easier to review and comment on ? I should be able to review it tonight.

[tivek]

@MatthieuDartiailh, I’m slowly hacking away on this. The GPIB-events branch is still not ready but event-related calls from PyVisaLib to Session objects have been wired through. Also, some preliminary support for GPIB events is in with some timeout-related bugs left to squash. Next is making events proper objects with .close(), .get_attribute() etc.

This seems to be a good time to ask for some feedback.

In particular, I wonder about storing event objects in its separate dict, PyVisaLibrary.events, as opposed to .sessions with which they share the pool of handles: https://github.com/tivek/pyvisa-py/blob/9f19bc992e89ae9c16f0a8af1090027cbb54edbd/pyvisa-py/highlevel.py#L103.

Also, I would like to hear your thoughts on ways to implement Attribute.in_resource() for event-related attributes. As it is now, attributes seem to expect sessions only.