> Vinay Sajip <vinay_sajip@yahoo.co.uk> added the comment:
>
>> But the cache needs to be invalidated when `exc_info` is changed -
>> as in set to None when it was a traceback object.
>
> When does the exc_info change for a record? AFAIK it's set when you
> create a LogRecord, and that's it.

Ok.

> To be honest, I'm not sure why you need that specific recipe. Notice
> the comment made by a user against the recipe.

I've responded as well .. that will explain why I need this specific  
recipe.

> But if you are set on
> doing it like this, then suppose I configure as follows:
>
> Create a StreamHandler(sys.stderr) and a StreamHandler(sys.stdout).
> Create a Formatter and attach it to the output handler.
> Create a Formatter with the format string used above but with
> an "error:" prefix, and attach it to the error handler.
> Add a Filter to each handler. This can be a single Filter class which
> either passes everything above a threshold or everything below a
> threshold. This will only have a few lines of code. Attach two such
> instances, suitably configured, to the appropriate handlers.
> Attach both handlers to the root logger (or some other logger).
>
> How will this differ in its effect from your recipe?

Actually, I did not know about 'Filter' until now. I will give it a try  
sometime.