Why does python logging module use old string formatting?

Question

Python has two main string formatting options % and str.format. logging module has a lazy feature.

logging.debug('The value is %s', huge_arg)

This does not construct the string if the log line is not going to be print. However, this feature works only if the sting uses old style % format. Is there a way to use str.format with this lazy feature? There could be a named arg like:

logging.debug('The value is {}', fmt_arg=(huge_arg))

Answer 1

The only answer to your question is that - so far - nobody has volunteered to change the logging code to support the newer format feature. If you're volunteering, why not ask about it on the Python-Dev mailing list? I expect it's trickier than you realize (e.g., there may be calls to logging functions already that happen to pass a fmt_arg keyword argument). Good luck ;-)