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| -rw-r--r-- | Doc/howto/logging-cookbook.rst | 55 |
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diff --git a/Doc/howto/logging-cookbook.rst b/Doc/howto/logging-cookbook.rst index e77e730..ecfab42 100644 --- a/Doc/howto/logging-cookbook.rst +++ b/Doc/howto/logging-cookbook.rst @@ -2033,3 +2033,58 @@ A couple of extra points to note: information on how logging supports using user-defined objects in its configuration, and see the other cookbook recipe :ref:`custom-handlers` above. + +.. _custom-format-exception: + +Customized exception formatting +------------------------------- + +There might be times when you want to do customized exception formatting - for +argument's sake, let's say you want exactly one line per logged event, even +when exception information is present. You can do this with a custom formatter +class, as shown in the following example:: + + import logging + + class OneLineExceptionFormatter(logging.Formatter): + def formatException(self, exc_info): + """ + Format an exception so that it prints on a single line. + """ + result = super(OneLineExceptionFormatter, self).formatException(exc_info) + return repr(result) # or format into one line however you want to + + def format(self, record): + s = super(OneLineExceptionFormatter, self).format(record) + if record.exc_text: + s = s.replace('\n', '') + '|' + return s + + def configure_logging(): + fh = logging.FileHandler('output.txt', 'w') + f = OneLineExceptionFormatter('%(asctime)s|%(levelname)s|%(message)s|', + '%d/%m/%Y %H:%M:%S') + fh.setFormatter(f) + root = logging.getLogger() + root.setLevel(logging.DEBUG) + root.addHandler(fh) + + def main(): + configure_logging() + logging.info('Sample message') + try: + x = 1 / 0 + except ZeroDivisionError as e: + logging.exception('ZeroDivisionError: %s', e) + + if __name__ == '__main__': + main() + +When run, this produces a file with exactly two lines:: + + 28/01/2015 07:21:23|INFO|Sample message| + 28/01/2015 07:21:23|ERROR|ZeroDivisionError: integer division or modulo by zero|'Traceback (most recent call last):\n File "logtest7.py", line 30, in main\n x = 1 / 0\nZeroDivisionError: integer division or modulo by zero'| + +While the above treatment is simplistic, it points the way to how exception +information can be formatted to your liking. The :mod:`traceback` module may be +helpful for more specialized needs. |