import usb, usb.core, usb.util, usb.backend.libusb1

...snippet...

#    usb.core.find()
# find our device

dev = usb.core.find(idVendor= ...., idProduct= ....)
#dev_1 = usb.util.find_descriptor(cfg, find_all =True)

# was it found?
if dev is None:
    raise ValueError('Device not found')

#x = dev.set_configuration()
#print (dev)
#print (help(usb.core))
if usb.core.find(find_all=True, bDeviceClass=7) is None:
    raise ValueError('No printer found')