Can't pickle local object 'CDLL.__init__.._FuncPtr'解法

 以下Error Message:

  File "app.py", line 624, in instrument_ready
    pickle.dump(visa_values_instruments_to_dump, f)
AttributeError: Can't pickle local object 'CDLL.__init__.<locals>._FuncPtr'

可能原因在於DLL相關的東西，無法pickle.

解法：將__init__()中可能包到的DLL，在其它函式再呼叫。

class VisaInstrument(Instrument):

    dll_32 = 'C:/Windows/System32/visa32.dll'

    def __init__():

        ...

        #將self.rm改成注解

        #self.rm = visa.ResourceManager(self.dll_32)

        ...

...

 def open(self):

        try:

            #self.dev = self.rm.open_resource(self.visa_addr)

            import pyvisa as visa # Simon added 20211108

            self.dev = visa.ResourceManager(self.dll_32).open_resource(self.visa_addr)

            ...

        except Exception as ex:

            return False

        else:

            return True