[pyusb-users] pyusb logging and errors behavior

[chris c. <cl...@gm...>]

I know pyusb (in svn) is currently not really supported/ready but I have a
usability question/observation.

If I have a (dumb) example script that uses the "basic" logging settings and
pyusb fails to load a backend the OpenUSB load attempt ends up being logged
when it too fails, a traceback is also dumped (the script keeps on going).

Example script and output

## -------------------- cut here --
"""List usb devices using basic logging.
This shows conflicts with pyusb logging implementation.

"""


import logging

do_logging = True  # And demo problem
#do_logging = False  # Pick one :)

log = logging

if do_logging:
    log.info('hello from test app, no more logging wil be issued form this
script')

import usb.core
import usb.util

import usb.backend.libusb10


# Monkey patch libusb10 away, or simply run on a machine without libusb10
def fake_get():
    return None

usb.backend.libusb10.get_backend = fake_get

for dev in usb.core.find(find_all=True):
    print dev
## -------------------- cut here --

## -------------------- cut here --
ERROR:usb.backend.openusb:Error loading OpenUSB backend
Traceback (most recent call last):
  File "/home/clach04/dev/python/usb/pyusb/trunk/usb/backend/openusb.py",
line 598, in get_backend
    _lib = _load_library()
  File "/home/clach04/dev/python/usb/pyusb/trunk/usb/backend/openusb.py",
line 148, in _load_library
    raise OSError('USB library could not be found')
OSError: USB library could not be found
<usb.core.Device object at 0x9d4f84c>
<usb.core.Device object at 0x9d4f8cc>
<usb.core.Device object at 0x9d4f92c>
<usb.core.Device object at 0x9d4f96c>
<usb.core.Device object at 0x9d4f9ac>
<usb.core.Device object at 0x9d4f9ec>
<usb.core.Device object at 0x9d4fa2c>
<usb.core.Device object at 0x9d4fa6c>
## -------------------- cut here --

is there a way to disable this behavior? I'm guessing this is some debug
code that is causing this. There are 2 issues:

1) the back trace that gets dumped out
2) the error gets logged (without logging for the usb.backend.openusb logger
being (explictly) turned on by the caller.


#2 is probably fixable by explicitly setting a log level (of off) in the
pyusb code. I could look into doing that if it would be helpful.

The workarounds are:

1) Don't use the basic logger in a user script, e.g. add something like; log
= logging.getLogger('mylogger') to the user script
2) use libusb10

It isn't a huge issue but a little odd.

Thanks!

Chris