logging module: problem with custom handlers

[Andreas Jung]

I am trying to write a custom logger with a custom handler:

class MyHandler(StreamHandler):
pass

class Logger:

def __init__(self):
self._l = logging.getLogger('someident')
self._l.addHandler(MyHandler('/path/to/logfile'))

Now I want to configure this logger through a configuration
file. How can I refer to the new handler in the configuration file?
Something like "class=MyHandler" did not work.

Any ideas?

Thanks,
Andreas

[wolf]

Andreas Jung <li...@andreas-jung.com> wrote in message news:<mailman.130.1067255...@python.org>...

> I am trying to write a custom logger with a custom handler:

you will have to be a tad more specific, i´m afraid. what does your
file layout look like? assuming that you have ::

fx.py
class X:
...

fy.py
class Y:
...
y = Y()

then, in order to refer to X, Y, or y from a third file, you can do
something like ::

from fx import X
from fy import Y
from fy import y

or ::

import fx.X

or ::

import fx.X as foo

there. does that help?

_wolf

[Peter Otten]

Andreas Jung wrote:

> I am trying to write a custom logger with a custom handler:

> Now I want to configure this logger through a configuration
> file. How can I refer to the new handler in the configuration file?
> Something like "class=MyHandler" did not work.
>
> Any ideas?

The handler's class is evaluatated like so in module logging.config:

klass = eval(klass, vars(logging))

For this to succeed you could do something like:

import logging
import logging.config

class MyHandler(logging.StreamHandler):
pass

logging.MyHandler = MyHandler

logging.config.fileConfig("test.cfg")
lgr = logging.getLogger("test")

lgr.info("Hello world")

where the relevant handler section has the line

class=MyHandler

I do not know if there is an "official" way to achieve the same, but then,
why would you build your own Handler in the first place?

Peter

[Neil Padgen]

>>>>> "Peter" == Peter Otten <__pet...@web.de> writes:

Peter> I do not know if there is an "official" way to achieve the
Peter> same, but then, why would you build your own Handler in the
Peter> first place?

I've just done exactly the same approach (independently), because of a
need to build two Handlers of my own. One is to avoid tracebacks
being logged with a SysLogHandler (it makes the syslog messages too
long, so nothing is logged), and the other is a subclass of
SMTPHandler which changes the subject of the mail if an exception of a
certain type is raised. [1]

I can think of plenty of other instances where building a custom
Handler is needed; for example, an SQLHandler which might log messages
to a database.

[1] This might be better done with a different Formatter, but getting
a custom Formatter to be used by logging.config is much harder than a
custom Handler, due to logging.Formatter() being called from within
logging.config.fileConfig().

Personally I think logging.config.fileConfig() is in need of some
serious refactoring... if only I had time to look into it!

-- Neil