Bugs item #1164953, was opened at 2005-03-17 02:38
Message generated for change (Comment added) made by vsajip
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1164953&group_id=5470
Category: Python Library
Group: None
>Status: Closed
>Resolution: Invalid
Priority: 5
Submitted By: logistix (logistix)
Assigned to: Vinay Sajip (vsajip)
Summary: logging.basicConfig creates phantom handler
Initial Comment:
calling logging.basicConfig() creates a phantom handler
that doesn't operate in an intuitive way. A reproducable
follows.
My actual use case: I started off using the logging
module on a project with the builting logging.info(),
logging.debug(), logging.error() functions. As my needs
got more sophisticated, I started creating some loggers
via logging.getLogger('a.b.c') I setup a custom handler
to do formatting without printing "INFO:a.b.c" headers.
One of my import statements triggered a call to
logging.basicConfig. Halfway through the running
program, my logging messages started showing up
twice. Once without the header and once with. I
eventually tracked this down to usage of a logging.info()
statement. I tried explicitly calling logging.basicConfig
(level=logging.ERROR) to disable the duplicate errors,
but that didn't work.
A trivial patch is attached. It fixes the problem if you
explicitly call logging.basicConfig. I don't know if it will
fix the implicit calls by logging.info(), etc.
C:\Python24>python
Python 2.4 (#60, Nov 30 2004, 11:49:19) [MSC v.1310
32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more
information.
>>> import logging
>>>
>>> logger = logging.getLogger('foo')
>>> logger.setLevel(logging.INFO)
>>> logger.info('bar') # no output yet
No handlers could be found for logger "foo"
>>>
>>> console = logging.StreamHandler()
>>> console.setLevel(logging.INFO)
>>> console.setFormatter(logging.Formatter("%
(message)s")
... )
>>> logger.addHandler(console)
>>>
>>> logger.info('foo')
foo
>>>
>>> logger.warning('foo')
foo
>>>
>>> logger.debug('foo')
>>>
>>> logger.info('foo')
foo
>>>
>>> logging.basicConfig(level=logging.ERROR)
>>>
>>> logger.info('foo')
foo
INFO:foo:foo
>>> ^Z
C:\Python24>
----------------------------------------------------------------------
>Comment By: Vinay Sajip (vsajip)
Date: 2005-03-17 10:52
Message:
Logged In: YES
user_id=308438
Thanks for the feedback, but it's not a bug. Check the
docstring for basicConfig: "This function does nothing if the
root logger already has handlers configured. It is a
convenience method intended for use by simple scripts to do
one-shot configuration of the logging package. The default
behaviour is to create a StreamHandler which writes to
sys.stderr, set a formatter using the BASIC_FORMAT format
string, and add the handler to the root logger."
The logging.debug(), etc. methods are for simple use of the
logging package. If you are using named loggers, then don't
use basicConfig() except to configure a handler at the root
level - and do this early in your application. Thereafter you
can log to the root logger (using logging.debug() and its
brethren) or to a named logger which has no handlers set (the
root's handlers will be used).
If you add a console handler manually to logger "foo" and
then add another one to the root handler via basicConfig(),
then both handlers will be called (correctly). This is what you
are seeing.
Your fix (add the level to the handler as well) does not fit the
contract of basicConfig(). Users working in simple mode will
just use the logger's level. Setting levels in the handler is for
more sophisticated use of the logging package than implied
by use of basicConfig() and logging.debug(), etc.
----------------------------------------------------------------------
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