[Python-Dev] Redirecting warnings.showwarning to logging (original) (raw)

Vinay Sajip vinay_sajip at yahoo.co.uk
Tue Nov 25 10:00:43 CET 2008

Based on feedback here, I have a slightly revised proposal. Scott makes the point that if the file parameter passed in to showwarning is not None, the caller may be trying to extract output formatting. So, it's not enough just to assign warnings.showwarning = logging.showwarning, since access to the original warnings.showwarning may be needed. So, the public API in logging would be

def captureWarnings(capture): """ If capture is true, redirect all warnings to the logging package. If capture is False, ensure that warnings are not redirected to logging but to their original destinations. """

Another new function, _showwarning( message, category, filename, lineno[, file [, line]]) will be added to the logging package. This implementation of showwarning will first check to see if the file parameter is None. If a file is specified, it will delegate to the original warnings implementation of showwarning. Otherwise, it will call warnings.formatwarning(message, category, filename, lineno[, line]) and will log the resulting string to a warnings logger named "py.warnings" [1] with level logging.WARNING. In order to configure logging of warnings to any particular destination, the logging configuration code will need to add appropriate handlers to the warnings logger. The precise format of the logging message will be determined by the logging configuration in effect, i.e. any formatters configured for the handlers attached to the logger.

I hope this covers everything, but please tell me if that's not the case.

Regards,

Vinay Sajip

[1] http://mail.python.org/pipermail/python-dev/2004-October/049282.html

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