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logging.md

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Logging

  • Multiple levels
  • Dynamic control
  • Tracebacks
  • Higher-level combination with asserts

Presenter notes

  • Here's just a high-level view of some of the benefits of logging

Logging levels

  • Levels: exception, critical, warning, info...
  • Temporarily cut down on debug noise
  • Send levels to multiple locations

Dynamic control

  • Change log level dynamically
  • Important with alternative distribution
    • Pyinstaller, py2exe

Presenter notes

  • Read log level from database/config file
  • Dynamic control is big step over asserts
  • Important b/c restarting interpreter could lose state/debug scenario

Tracebacks

  • Built-in with exception level
  • Invaluable in error scenarios

Logging + asserts

  • Log assertions to different file/database
  • Lots of data-mining capabilities

Presenter notes

  • Build a low-fi analytics system by logging to database, network file, dropbox
  • Shell scripts to collect simple text files
  • Track what features people use

Logging + asserts

!python
def main():
    logging.basicConfig(level=logging.WARNING)
    log = logging.getLogger('example')
    try:
        throws()
        return 0
    except AssertionError:
        log.debug('Error: %s' % (err))
    except Exception as err:
        log.exception('Error from throws():')
        return 1

Logging downsides

Presenter notes

  • Two CS problems, naming and caching
  • Levels == naming
  • Be careful/mindful logging could be your best defense against a production bug