python loggingL filter limitation, looks intentional?

Chris Withers chris at
Mon Jan 16 13:39:57 EST 2012

Hi Vinay,

On 16/01/2012 15:08, Vinay Sajip wrote:
> Filtering is intended to be for cases where integer level-based filtering is insufficient;

...or where you want to manipulate log messages, which is the use case I 

> You are right that you would need to add a filter to all of the loggers where you want it to apply, or to all of the handlers where you want it to apply.

Why is this? There must be some rationale for this rather than what, for 
me and others I've talked to, would seem more natural, ie: a filter on 
the root logger would get messages both logged to it and any messages 
propagated to it from child loggers to process.

> However, if you find your usage pattern occurring very commonly in your applications, it's easy enough to create a DelegatingHandler handler class which passes its events on to any number of handlers you like.

But this is just extra work when the normal built-in 
delegation-upwards-ending-in-root works exactly as I want.

It's also the opposite of what I'd need, I'd need to plug one handler 
into all the specific loggers that get used (and bear in mind that many 
libraries log to __name__ from modules and sub-modules) this is a pretty 
onerous task :-(



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