| msg21717 - (view) |
Author: Roy Smith (roysmith) |
Date: 2004-07-20 10:28 |
| I am running: Roy-Smiths-Computer:unit$ uname -a Darwin Roy-Smiths-Computer.local 7.4.0 Darwin Kernel Version 7.4.0: Wed May 12 16:58:24 PDT 2004; root:xnu/xnu -517.7.7.obj~7/RELEASE_PPC Power Macintosh powerpc Roy-Smiths-Computer:unit$ py Python 2.3.4 (#3, Jun 29 2004, 21:48:03) [GCC 3.3 20030304 (Apple Computer, Inc. build 1495)] on darwin Type "help", "copyright", "credits" or "license" for more information. --------- #!/usr/bin/env python import logging logger = logging.getLogger () logger.error ('one') logger.error ('two') --------- The above program prints (to stderr): --------- No handlers could be found for logger "root" --------- 6.28 logging -- Logging facility for Python says, "Each logger can have zero, one or more handlers associated with it". It doesn't explicitly says what happens when there are zero handlers, but I would expect that any messages would just be silently ignored. Printing a warning to stderr is definately the WRONG thing to do. |
|
|
| msg21718 - (view) |
Author: Vinay Sajip (vinay.sajip) *  |
Date: 2004-07-21 14:24 |
| Logged In: YES user_id=308438 This is not a bug. In general, the logging module does not print spurious error messages - however, in the case where no handlers are configured at all, then this is considered a possible configuration error and a single message is printed. Note that log4j does this too - it's not peculiar to Python logging. Note that logged messages are not printed - only the single warning indicating a possible configuration problem. |
|
|
| msg21719 - (view) |
Author: Roy Smith (roysmith) |
Date: 2004-07-21 14:45 |
| Logged In: YES user_id=390499 I disagree. I don't think it should be considered an error to have a logger with no handlers configured (especially since the documentation explicitly states that it's allowed). The logic here is that every handler gets a chance to process the message; there's nothing magic about the list of handlers being empty. Here's where this came up: I've got a class I'm testing. I embedded some logger.debug () calls in it. Most of the time I don't even want to see those calls. Sure, I could create a logger handler, and set a level which ignores debug calls, but that forces every user of my class to do that. If a logger with no handlers attached just silently drops all messages, the user doesn't even have to know about the logging calls in my class. Even if you were to decide to enforce that a logger must have at least one handler, then the error should be signified the way all other python errors are -- by throwing an exception. And, of course, you should update the documention to match. But, I think this would be the wrong approach. Just eliminating the message to stderr would be (IMHO) the right thing to do. |
|
|
| msg21720 - (view) |
Author: Roy Smith (roysmith) |
Date: 2004-07-21 14:45 |
| Logged In: YES user_id=390499 I disagree. I don't think it should be considered an error to have a logger with no handlers configured (especially since the documentation explicitly states that it's allowed). The logic here is that every handler gets a chance to process the message; there's nothing magic about the list of handlers being empty. Here's where this came up: I've got a class I'm testing. I embedded some logger.debug () calls in it. Most of the time I don't even want to see those calls. Sure, I could create a logger handler, and set a level which ignores debug calls, but that forces every user of my class to do that. If a logger with no handlers attached just silently drops all messages, the user doesn't even have to know about the logging calls in my class. Even if you were to decide to enforce that a logger must have at least one handler, then the error should be signified the way all other python errors are -- by throwing an exception. And, of course, you should update the documention to match. But, I think this would be the wrong approach. Just eliminating the message to stderr would be (IMHO) the right thing to do. |
|
|
| msg178545 - (view) |
Author: Terry J. Reedy (terry.reedy) * |
Date: 2012-12-30 00:10 |
| Update: It appears that in at least 3.2+ (but not 2.7), loggers have a default handler, making the no-handler behavior moot. In any case, the example code prints 'one' and 'two' instead of the message. |
|
|