Class LoggingConfigurable

traitlets/config/configurable.py:465–511

A parent class for Configurables that log. Subclasses have a log trait, and the default behavior is to get the logger from the currently running Application.

class LoggingConfigurable(Configurable):
    """A parent class for Configurables that log.

    Subclasses have a log trait, and the default behavior
    is to get the logger from the currently running Application.
    """

    log = Any(help="Logger or LoggerAdapter instance", allow_none=False)

    @validate("log")
    def _validate_log(self, proposal: Bunch) -> LoggerType:
        if not isinstance(proposal.value, (logging.Logger, logging.LoggerAdapter)):
            # warn about unsupported type, but be lenient to allow for duck typing
            warnings.warn(
                f"{self.__class__.__name__}.log should be a Logger or LoggerAdapter,"
                f" got {proposal.value}.",
                UserWarning,
                stacklevel=2,
            )
        return t.cast(LoggerType, proposal.value)

    @default("log")
    def _log_default(self) -> LoggerType:
        if isinstance(self.parent, LoggingConfigurable):
            assert self.parent is not None
            return t.cast(logging.Logger, self.parent.log)
        from traitlets import log

        return log.get_logger()

    def _get_log_handler(self) -> logging.Handler | None:
        """Return the default Handler

        Returns None if none can be found

        Deprecated, this now returns the first log handler which may or may
        not be the default one.
        """
        if not self.log:
            return None
        logger: logging.Logger = (
            self.log if isinstance(self.log, logging.Logger) else self.log.logger
        )
        if not getattr(logger, "handlers", None):
            # no handlers attribute or empty handlers list
            return None
        return logger.handlers[0]


CT = t.TypeVar("CT", bound="SingletonConfigurable")