How can I get formatter string from a logging.formatter object in Python?

Question

Hi I want to make a logging manager gui. Basically I want to get the tree structure of loggers and show their level and formatter in a pyqt gui. How can I get the format string from a formatter associated a handler object?

eg:

import logging
_logger = logging.getLogger('myLogger')

ch = logging.StreamHandler()
ch.setLevel(logging.INFO)
formatter = logging.Formatter('%(name)s:%(levelname)s: %(message)s')
ch.setFormatter(formatter)
_logger.addHandler(ch)
_logger.propagate=0

Now I have the _logger, how can I get string '%(name)s:%(levelname)s: %(message)s' from the logging.Formatter object?

>>> _logger.handlers[0]
<logging.StreamHandler object at 0x13807610>
>>> _logger.handlers[0].formatter
<logging.Formatter object at 0x13807690>

Answer 1

logging.Formatter instances have a _fmt attribute:

>>> _logger.handlers[0].formatter
<logging.Formatter object at 0x102c72fd0>
>>> _logger.handlers[0].formatter._fmt
'%(name)s:%(levelname)s: %(message)s'

You can always use dir() and vars() on objects to see what names might be available:

>>> vars(_logger.handlers[0].formatter)
{'datefmt': None, '_fmt': '%(name)s:%(levelname)s: %(message)s'}

or you could just look at the source code (linked from the top of the module documentation).