python_packaging/src/gmxapi/_logging.py

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  34
  35 """Python logging facilities use the built-in logging module.
  36
  37 Upon import, the gmxapi package sets a placeholder "NullHandler" to block
  38 propagation of log messages to the root logger (and sys.stderr, if not handled).
  39
  40 If you want to see gmxapi logging output on sys.stderr, attach a
  41 logging.StreamHandler to the 'gmxapi' logger.
  42
  43 Example::
  44
  45     ch = logging.StreamHandler()
  46     # Optional: Set log level.
  47     ch.setLevel(logging.DEBUG)
  48     # Optional: create formatter and add to character stream handler
  49     formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
  50     ch.setFormatter(formatter)
  51     # add handler to logger
  52     logging.getLogger('gmxapi').addHandler(ch)
  53
  54 To handle log messages that are issued while importing :py:mod:`gmxapi` and its submodules,
  55 attach the handler before importing :py:mod:`gmxapi`
  56
  57 Each module in the gmxapi package uses its own hierarchical logger to allow
  58 granular control of log handling (e.g. ``logging.getLogger('gmxapi.operation')``).
  59 Refer to the Python :py:mod:`logging` module for information on connecting to and handling
  60 logger output.
  61 """
  62
  63 __all__ = ['logger']
  64
  65 # Import system facilities
  66 from logging import getLogger, DEBUG, NullHandler
  67
  68 # Define `logger` attribute that is used by submodules to create sub-loggers.
  69 logger = getLogger('gmxapi')
  70 # Prevent gmxapi logs from propagating to the root logger (and to sys.stderr)
  71 # if the user does not take action to handle logging.
  72 logger.addHandler(NullHandler(level=DEBUG))
  73 logger.info("Importing gmxapi.")