How to prevent logging warning?

Thomas Heller theller at python.net
Wed Oct 5 16:10:06 CEST 2005


> Thomas Heller wrote:
>> I'm about to add some logging calls to a library I have.  How can I
>> prevent that the script that uses the library prints
>> 'No handlers could be found for logger "comtypes.client"' when the
>> script runs?
>> I would like to setup the logging so that there is no logging when
>> nothing is configured, and no warning messages are printed.

Maksim Kasimov <maksim.kasimov at gmail.com> writes:

> may be this you will find usefull:
>
> def getLog(logName, fileName = None):
>
>      if fileName:
>          hdl = logging.FileHandler(fileName)
>      else:
>          hdl = logging.StreamHandler()
>
>      fmt = logging.Formatter("%(name)s:\t%(levelname)s:\t%(asctime)s:\t%(message)s")
>      hdl.setFormatter(fmt)
>      log = logging.getLogger(logName)
>      log.addHandler(hdl)
>
>      return log

Not really - I know how to set up handlers, but I think it should be
optional. Assume I have

  log = logging.getLogger("comtypes.client")

and later

  log.warn("foo bar")

in the library code.

If I use the library an my script, I get the warning that I mentioned
above.  I want the script by default to be agnostic about the libraries
logging.  When I want to see the log messages, I can always do

  logging.basicConfig()

in the script to see the log messages.

I get the behaviour that I want when I add a 'NULL' handler in the
library, but is this really how logging is intended to be used?

<library>
log = logging.getLogger("comtypes.client")

class NULLHandler(logging.Handler):
    def emit(self, *args):
        pass

log.addHandler(NULLHandler())
</library>

Thomas



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