Example, "filters": ["filter_dep","throttle"]. Can one handler (or one logger) use multiple filters?

Question

Python

LOGGING = {
    'version': 1,
    'disable_existing_loggers': True,
    'formatters': {
        'verbose': {
            'format': '%(levelname)s %(asctime)s %(module)s %(process)d %(thread)d %(message)s'
        },
        'simple': {
            'format': '%(levelname)s %(message)s'
        },
    },
    'filters': {
        'special': {
            '()': 'project.logging.SpecialFilter',
            'foo': 'bar',
        }
    },
    'handlers': {
        'null': {
            'level': 'DEBUG',
            'class': 'logging.NullHandler',
        },
        'console':{
            'level': 'DEBUG',
            'class': 'logging.StreamHandler',
            'formatter': 'simple'
        },
        'mail_admins': {
            'level': 'ERROR',
            'class': 'django.utils.log.AdminEmailHandler',
            'filters': ['special']
        }
    },
    'loggers': {
        'django': {
            'handlers': ['null'],
            'propagate': True,
            'level': 'INFO',
        },
        'django.request': {
            'handlers': ['mail_admins'],
            'level': 'ERROR',
            'propagate': False,
        },
        'myproject.custom': {
            'handlers': ['console', 'mail_admins'],
            'level': 'INFO',
           <b> 'filters': ['special']</b>
        }
    }
}

Answer 1

Technically, both Logger and Handler classes are descendants of Filterer.

Take a look at the sources.

class Filterer(object):
    """
    A base class for loggers and handlers which allows them to share
    common code.
    """
    def __init__(self):
        """
        Initialize the list of filters to be an empty list.
        """
        self.filters = []

    def addFilter(self, filter):
        """
        Add the specified filter to this handler.
        """
        if not (filter in self.filters):
            self.filters.append(filter)
# ...

In general, looking at the source code is much more useful for self-development than asking.
It shows that any filter can contain nested filters.

All nested filters must return True for the filter to return True.

def filter(self, record):
        """
        Determine if a record is loggable by consulting all the filters.

        The default is to allow the record to be logged; any filter can veto
        this and the record is then dropped. Returns a zero value if a record
        is to be dropped, else non-zero.

        .. versionchanged:: 3.2

           Allow filters to be just callables.
        """
        rv = True
        for f in self.filters:
            if hasattr(f, 'filter'):
                result = f.filter(record)
            else:
                result = f(record) # assume callable - will raise if not
            if not result:
                rv = False
                break
        return rv

That is, filters work through a logical "AND".
Well, yes, maybe.