Python context manager cum decorator to log execution time

exectimelog.py

import logging
from time import perf_counter
from contextlib import ContextDecorator


class exectimelog(ContextDecorator):
    def __init__(self, msg='Elapsed time', logger=None):
        self.msg = msg
        self.logger = logger or logging.getLogger(__name__)

    def __enter__(self):
        self.start_time = perf_counter()
        return self

    def __exit__(self, *args):
        self.end_time = perf_counter()
        self.elapsed_time = self.end_time - self.start_time
        self.logger.warning('%s: %.3fs', self.msg, self.elapsed_time)
        return False

exectimelog_example.py

# as decorator
@exectimelog()
def myf():
    # do stuff

# as context manager
with exectimelog():
    # do stuff