Decorator to make function log calls for later examination

call_logger.py

#!/usr/bin/env python

from dataclasses import dataclass
from datetime import datetime, timedelta
from functools import update_wrapper


@dataclass(frozen=True)
class Call:
    func: callable
    call_time: datetime
    duration: timedelta
    args: list
    kwargs: dict
    result: any = None
    exception: Exception = None

    def __repr__(self):
        fn = self.func.__name__
        ct = str(self.call_time)
        d = str(self.duration)
        a = self.args
        kw = self.kwargs
        r = f"[{str(self.result)}]" if self.result else self.result
        e = f"[{self.exception}]" if self.exception else self.exception
        return f"Call(func={fn}, call_time={ct}, duration={d}, " \
               f"args={a}, kwargs={kw}, result={r}, exception={e}"


class log_calls:
    """Make the decorated function log all calls to it"""

    def __init__(self, func):
        self.func = func
        self.calls: list[Call] = []
        update_wrapper(self, func)

    def __call__(self, *args, **kwargs):
        exc = None
        start = datetime.utcnow()
        try:
            result = self.func(*args, **kwargs)
        except Exception as ex:
            exc = ex
        duration = datetime.utcnow() - start
        if exc:
            self.calls.append(Call(self.func, start, duration, args, kwargs, None, exc))
            raise exc
        else:
            self.calls.append(Call(self.func, start, duration, args, kwargs, result, None))
            return result


if __name__ == '__main__':

    @log_calls
    def greet(name: str):
        if name in ['Sadie', 'Bently']:
            raise ValueError("Pets can't be greeted.")
        return f"Why hello, {name}."

    @log_calls
    def farewell(name: str):
        return f"See you next time {name}."


    print(f"Making attempts to call\n{'-'*80}")
    for p in ['Steve', 'Sadie', 'Jen']:
        try:
            print(greet(p))
            print(farewell(p))
        except Exception as ex:
            print('SOMETHING TERRIBLE HAPPENED!', ex)

    print(f"\nGreeting call log\n{'-'*80}")
    for c in greet.calls:
        print(c)

    print(f"\nFarewell call log\n{'-'*80}")
    for c in farewell.calls:
        print(c)