[pyusb-users] ValueError: No backend available

[Bruce L. <bru...@gm...>]

Good morning ..

I have an iMac 7.1 running OS X Mavericks and use Enthought Canopy to run
Python.
I want to use Python to read data from and write data to USB ports.
I have used MacPorts to install PyUSB and libusb using their portfiles.
>From Idle I have run...

import usb.core
import usb.util
dev = usb.core.find(find_all=True)

and receive the following error...

Traceback (most recent call last):
  File "<pyshell#5>", line 1, in <module>
    dev = usb.core.find(find_all=True)
  File "/Library/Python/2.7/site-packages/usb/core.py", line 867, in find
    raise ValueError('No backend available')
ValueError: No backend available

I have trawled through the various web sites that identify this error and I
have been unable to resolve the problem.
Does anyone please have a solution?

Thanks ... Bruce