CODEWITHSUNDEEP
python-2.7kivypyusb
YvonneH
YvonneH

Reputation: 75

kivy .bind results in AssertionError: '' is not callable

I am writing a GUI in Linux using Kivy and Python. The program should detect a USB device and using the device to program an image to a target. Here are a snippet of my code:

These are the codes I am trying to detect USB device. This is on a file, let's call it A.py.

    busses = usb.busses()

    for bus in busses:
        devices = bus.devices
        for dev in devices:
            if (dev.idVendor == vendor and dev.idProduct == product):
                    obj = ProgJTAG.ProgJTAG(bus.dirname,dev.filename, dev.idVendor, dev.idProduct, dev)

                    break

When I ran the program, assertion error occured in creating an instance of ProgJTAG. This is defined in a separate file ProgJTAG.py as follows:

  class ProgJTAG(BoxLayout):
    usb_bus = StringProperty('')
    usb_dev = StringProperty('')
    usb_vendor = StringProperty('')
    usb_product = StringProperty('')

    def __init__(self, _usb_bus, _usb_dev, _usb_vendor, _usb_product, dev):
          super(ProgJTAG, self).__init__()

          self.usb_bus = _usb_bus
          self.usb_dev = _usb_dev
          self.usb_vendor = str(_usb_vendor)
          self.usb_product = str(_usb_product)
          self.bind(usb_bus=self.usb_bus)
          self.bind(usb_dev=self.usb_bus)
          self.bind(usb_vendor=self.usb_bus)
          self.bind(usb_product=self.usb_bus)

The error occur from the line self.bind(usb_bus=self.usb_bus). The error message is File "_event.pyx", kivy._event.EventDispatcher.bind(kivy/_event.c:5536) AssertionError: '' is not callable

Q1. Can anyone help what the assertion means?

Q2. I noticed that the _usb_bus and _usb_dev are empty string. Is this assertion caused by the fact that the _usb_bus and _usb_dev are empty string property hence not callable?

Upvotes: 0

Views: 1710

Answers (1)

inclement
inclement

Reputation: 29488

Yes, when you bind you must pass a function because the binding will try to call it later.

Upvotes: 1

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