python - How to log number with commas as thousands separators? -

the time has come convert prints logging calls in library i'm maintaining. of print calls using str.format, (simplified):

>>> n = 4000000 >>> print(f"this bird wouldn't voom if put {n:,} volts through it!") bird wouldn't voom if put 4,000,000 volts through it! 

when try log it:

>>> log.warning("this bird wouldn't voom if put %d, volts through it!", n) warning:root:this bird wouldn't voom if put 4000000, volts through it! 

seems not specifying thousands separator correctly. how specify thousands separator when using %-formatting syntax python's stdlib logging module necessitates?

currently using workaround, give desired output, seems wrong since variable formatted first using str.format , formatted string again, instead of logging number directly:

>>> log.warning("this bird wouldn't voom if put %s volts through it!", format(n, ',')) warning:root:this bird wouldn't voom if put 4,000,000 volts through it! 

that's limitation logging , it's mentioned in (at least 1 place in) documentation:

logging.debug(msg, *args, **kwargs)

logs message level debug on root logger. msg message format string, , args arguments merged msg using string formatting operator. (note means can use keywords in format string, single dictionary argument.)

(emphasis mine)

but string formatting operator % doesn't support thousand seperators.

you adapt recipe official cookbook:

import logging  class message(object):     def __init__(self, fmt, args):         self.fmt = fmt         self.args = args      def __str__(self):         return self.fmt.format(*self.args)  class styleadapter(logging.loggeradapter):     def __init__(self, logger, extra=none):         super(styleadapter, self).__init__(logger, or {})      def log(self, level, msg, *args, **kwargs):         if self.isenabledfor(level):             msg, kwargs = self.process(msg, kwargs)             self.logger._log(level, message(msg, args), (), **kwargs)  logger = styleadapter(logging.getlogger(__name__))  def main():     # changed     logger.warning("this bird wouldn't voom if put {:,} volts through it!", 4000000)  if __name__ == '__main__':     logging.basicconfig(level=logging.debug)     main() 

warning:__main__: bird wouldn't voom if put 4,000,000 volts through it!

this copied verbatim (i changed message) last example in "use of alternative formatting styles" section.

---

personally go format(n, ',') solution. may not perfect doesn't require setting custom loggeradapter print different thousand seperator.