Python default logger disabled

For some reason, in a Python application I am trying to modify, the logger is not logging anything. I traced the error to logging/__init__.py

def handle(self, record):
    """
    Call the handlers for the specified record.

    This method is used for unpickled records received from a socket, as
    well as those created locally. Logger-level filtering is applied.
    """
    if (not self.disabled) and self.filter(record):
        self.callHandlers(record)

I am not sure why, but self.disabled is True. Nowhere in the application this value is set and I don’t think any of the packages is changing it. The logger is instantiated as usual logger = logging.getLogger(__name__). When I set logger.disabled = False before actually logging anything (before calling logger.info()), the logger prints the expected log text. But if I don’t, it returns in handle() without logging anything.

Is there any way I can debug this? Perhaps one can change the Logger class so that some function is called whenever disabled gets written to…

Answer

If you need to trace what code might set handler.disabled to True (it is 0, so false, by default), you can replace the attribute with a property:

import logging
import sys

@property
def disabled(self):
    try:
        return self._disabled
    except AttributeError:
        return False

@disabled.setter
def disabled(self, disabled):
    if disabled:
        frame = sys._getframe(1)
        print(
            f"{frame.f_code.co_filename}:{frame.f_lineno} "
            f"disabled the {self.name} logger"
        )
    self._disabled = disabled

logging.Logger.disabled = disabled

Demo from the interactive interpreter:

>>> import logging
>>> logging.getLogger('foo.bar').disabled = True
<stdin>:1 disabled the foo.bar logger

If you want to see the full stack, add from traceback import print_stack, and inside the if disabled: block, print_stack(frame).