Customizable decorator logging the input, output, exception, and cost of a function call.

log_utils.py

import functools
import logging
import time


def log_func(
    logger: logging.Logger,
    *,
    log_input=True,
    input_level=logging.WARNING,
    log_output=False,
    output_level=logging.WARNING,
    log_timing=False,
    timing_level=logging.WARNING,
    log_exception=False,
    exception_level=logging.ERROR,
    timing_timer=time.perf_counter,
):
    def wrapper(fn):
        @functools.wraps(fn)
        def inner(*args, **kwargs):
            display_kwargs = tuple(f"{k}={v}" for k, v in kwargs.items())
            display_params = ", ".join([str(a) for a in args + display_kwargs])
            fn_message = "{}({})".format(fn.__name__, display_params)

            if log_timing:
                start_time = timing_timer()

            if log_input:
                logger.log(input_level, f"calling function: {fn_message}")

            if log_exception:
                try:
                    rv = fn(*args, **kwargs)
                except Exception as e:
                    logger.log(
                        exception_level,
                        f"exception in function: {fn_message} => {e.args}",
                        exc_info=e,
                    )
                    raise e
            else:
                rv = fn(*args, **kwargs)

            if log_output:
                logger.log(output_level, f"function called: {fn_message} => {rv}")

            if log_timing:
                cost = timing_timer() - start_time
                logger.log(timing_level, f"function costs: {fn_message} => {cost}")

            return rv

        return inner

    return wrapper