log_context.py

from contextlib import contextmanager
import logging

_log = logging.getLogger(__name__)


class MyFilter:
    def __init__(self, **kwargs):
        self.kwargs = kwargs

    def filter(self, record):
        record.msg += ' ' + ' '.join('{}={}'.format(k, v) for k, v in self.kwargs.items())
        return True


@contextmanager
def log_context(**kwargs):
    log_filter = MyFilter(**kwargs)
    root_logger = logging.getLogger()

    for handler in root_logger.handlers:
        handler.addFilter(log_filter)

    yield log_filter

    for handler in root_logger.handlers:
        handler.removeFilter(log_filter)


def f():
    _log.info('hi')


if __name__ == '__main__':
    logging.basicConfig(level='DEBUG', format='%(asctime)s %(name)s:%(lineno)d %(levelname)s %(message)s')
    f()
    with log_context(foo='bar'):
        f()
    f()