Customize Python log formatting by log level

customlog.py

"""
A simple example of formatting log messages differently based on their
Python log level. It seems a basic feature for a logging library that
as far as I can tell is missing from stdlib logging


So the usual route is overriding the logging.Formatter class as shown
below. Sovling the problem this way isn't novel or unusual as nearly
all of the stdblib classes are meant to be extended, but it would
be nice if you could just pass a dictionary of log levels and their
respective formats.

I've yet to find a "good" logging package on PyPi, let me know of any
you may know..

-AG

--
The behavior here that is modified:

* In the stdlib, CRITICAL and FATAL are actually the same log level.
  this Formatter will always print FATAL as the log level even when
  CRITICAL is used as the entry-point
* INFO level messages are essentially printed as if they were invoked
  using the `print` built-in, but still will be logged to file, or
  syslog, or wherever based on what logger you apply it to. Does
  an informational message have to either be completely ugly and
  full of debug info OR be absent from the logfile? If you use
  this approach you don't have to deal with the trade-off

Obviously, this can be used in any way, this is just an example

-AG
"""
import logging
class LevelBasedormatter(logging.Formatter):
    def __init__(self, fmt):
        logging.Formatter.__init__(self, fmt)

    def format(self, record):
        format_orig = self._fmt
        if record.levelname == "WARNING":
            record.levelname = "WARN"

        if record.levelno == logging.INFO:
            format_orig = self._fmt
            self._fmt = "%(message)s"
            r = logging.Formatter.format(self, record)
            self._fmt = format_orig
            return r
        elif record.levelno == logging.CRITICAL or record.levelno == logging.ERROR or record.levelno == logging.WARN:
            if record.levelno == logging.FATAL:
                record.levelname = "FATAL"
            self._fmt = "\n... %(levelname)s, %(message)s\n"
            r = logging.Formatter.format(self, record)
            return r
        else:
            return logging.Formatter.format(self, record)