Delete arbitrary waveform from memory raises AttributeError: '_SessionBase' object has no attribute '_clear_arb_waveform'

[ihouses]

• Description of issue

When deleting a arbitrary waveform the driver crashes with the error:
AttributeError: '_SessionBase' object has no attribute '_clear_arb_waveform'

My code is:

options = {'simulate': False, 'driver_setup': {'Model': '5433 (2CH)', 'BoardType': 'PXIe', }, }
self.session = nifgen.Session(resource_name=name, options=options)

def start_generation(self, delete_waveform=True):

    self.session._initiate_generation()

    if delete_waveform is True:
        self.session.channels[self.channel].delete_waveform(self.waveform_handle)

self.waveform_handle = 0

If I dont't delete the waveform I get an error:

nifgen.errors.DriverError: -1074118634: You must specify which waveform to generate.

But since : self.session._initiate_generation() doesn't have arguments to select the waveform that I want to initiate... I don't know how to do it.

I load my waveform with:

self.session.channels[channel].arb_sample_rate = self.sample_rate
self.session.channels[channel].output_mode = nifgen.OutputMode.ARB
self.session.channels[channel].trigger_mode = enums.TriggerMode.SINGLE
self.waveform_handle = self.session.create_waveform(waveform_data_array=waveform)

    self.session.streaming_waveform_handle = self.waveform_handle
    self.session.channels[channel].configure_arb_waveform(waveform_handle=self.waveform_handle, gain=1, offset=0)

I don't know how to overwrite and previous handler.

[marcoskirsch]

    self.session._initiate_generation()

You shouldn't use anything that starts with an underscore. Those methods are considered "private" and may change. Only use the methods and properties publicly documented. See this example.

If I dont't delete the waveform I get an error:

nifgen.errors.DriverError: -1074118634: You must specify which waveform to generate.

But since : self.session._initiate_generation() doesn't have arguments to select the waveform that I want to initiate... I don't know how to do it.

Set property arb_waveform_handle

This should be enough to get you unstuck. Regardless, this is a legitimate bug and we will fix it. Thanks for reporting!

[ihouses]

set arb_waveform_handle prevents to get the error.
Now I need to be able to delete waveforms from memory, I guess this is the fix that you are talking about.

[marcoskirsch]

nifgen.Session.delete_waveform() is a hand-coded method that calls either of the codegenerated methods _delete_named_waveform or _clear_arb_waveform. They eventually call the NI-FGEN functions on the DLL:

ViStatus _VI_FUNC  niFgen_ClearArbWaveform (
   ViSession vi,
   ViInt32 wfmHandle);

or

ViStatus _VI_FUNC niFgen_DeleteNamedWaveform(
   ViSession vi,
   ViConstString channelName,
   ViConstString wfmName);

Notice that niFgen_ClearArbWaveform doesn't take in a channel. So this cannot be made to work without adding new functionality to the driver runtime.

All this said, the error you get AttributeError: '_SessionBase' object has no attribute '_clear_arb_waveform' is terrible.

If instead of

        self.session.channels[self.channel].delete_waveform(self.waveform_handle)

you called the method directly on the session:

        self.session.delete_waveform(self.waveform_handle)

then it would work.