[Python-Dev] Using logging in the stdlib and its unit tests (original) (raw)

Vinay Sajip vinay_sajip at yahoo.co.uk
Wed Dec 8 09:51:44 CET 2010

Robert Kern <robert.kern gmail.com> writes:

I really don't understand how this view can be consistent with the practice of adding NullHandler to loggers. If this message is so important to prevent misconfiguration, then why should a library author decide to silence it for his users?

Because the application developer knows more about the end-user audience for their application, they are better placed to know how logging should work for their application. It's not an error for a particular application developer to decide that nothing should be produced by logging for a particular application; they (particularly when casual users) would be confused by the misconfiguration message due to logging by a library they're using.

The library author's users are the application developers who use the library, not the end users who use their applications. Sometimes they're the same people, I know, but I just think of them as wearing different hats :-)

[...] I strongly suspect that almost all configurations include a catch-all root logger and that most of those only consist of that root logger.

That doesn't seem right: your comment might be conflating loggers with handlers. The common pattern would be (or should be) to name loggers according to name in the modules which use logging, but only configure handlers for the root logger. That way, logging messages indicate their origin (because of the name convention) but you only need to add handlers at the root logger to capture all the logging information.

Same mistake. I intended the correction to apply to all such statements in my post.

Oh, right. I thought this was a different case.

I think that boilerplate should be minimized. If using getLogger() should almost always be followed by adding a NullHandler, then it should be the default behavior. The easiest way to achieve this effect is to simply not issue the warning message.

getLogger() should NOT "almost always be followed by adding a NullHandler". For example, in Django, only the logger named "django" would have that handler added; no other Django logger (e.g. "django.db.models") would need to have that handler added.

Regards,

Vinay Sajip

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