Python 3.12 ParamSpec example

common.py

import logging

# DEFAULT_LOG_FORMAT = "[%(asctime)s.%(msecs)03d] %(funcName)20s %(module)s:%(lineno)d %(levelname)-8s - %(message)s"
DEFAULT_LOG_FORMAT = (
    "%(funcName)10s %(module)s:%(lineno)d %(levelname)-8s - %(message)s"
)


def configure_logging(level: int = logging.INFO) -> None:
    logging.basicConfig(
        level=level,
        datefmt="%Y-%m-%d %H:%M:%S",
        format=DEFAULT_LOG_FORMAT,
    )

main.py

import logging
import random
from dataclasses import dataclass
from functools import wraps
from typing import Callable, reveal_type

from common import configure_logging

log = logging.getLogger(__name__)


@dataclass
class Counts:
    count: int = 0

    def inc(self) -> None:
        self.count += 1

    def dec(self) -> None:
        self.count -= 1


def trace[** P, T](
    *,
    sep: str = "*",
    size: int = 1,
) -> Callable[[Callable[P, T]], Callable[P, T]]:
    def decorator(func: Callable[P, T]) -> Callable[P, T]:
        count = Counts()

        @wraps(func)
        def wrapper(*args: P.args, **kwargs: P.kwargs) -> T:
            count.inc()
            log.info(
                "%s call %r with args %r and kwargs %r",
                sep * count.count * size,
                func.__name__,
                args,
                kwargs,
            )
            result = func(*args, **kwargs)
            log.info(
                "%s call %r result: %r",
                sep * count.count * size,
                func.__name__,
                result,
            )
            count.dec()
            return result

        return wrapper

    return decorator


@trace()
def fac(n: int) -> int:
    if n <= 2:
        return n
    return n * fac(n - 1)


@trace(sep="|", size=2)
def fib(n: int) -> int:
    if n < 2:
        return n

    return fib(n - 1) + fib(n - 2)


def stringify[** P, T](func: Callable[P, T]) -> Callable[P, str]:
    @wraps(func)
    def wrapper(*args: P.args, **kwargs: P.kwargs) -> str:
        return str(func(*args, **kwargs))

    return wrapper


@stringify
def random_number() -> int:
    return random.randint(1, 100)


# @stringify
def square(n: int) -> int:
    return n * n


def demo_trace() -> None:
    fac5 = fac(5)
    log.info("fac(5) = %s", fac5)
    log.warning("space")
    fac7 = fac(7)
    log.info("fac(7) = %s", fac7)

    log.warning("space bigger")

    fib3 = fib(3)
    log.info("fib(3) = %s", fib3)
    log.warning("space")
    fib4 = fib(4)
    log.info("fib(4) = %s", fib4)


def main() -> None:
    configure_logging()
    # demo_trace()

    number = random_number()
    reveal_type(number)
    sq = square(4)
    reveal_type(sq)


if __name__ == "__main__":
    main()

pyproject.toml

[tool.mypy]
strict = true

requirements.txt

mypy==1.14.1
mypy-extensions==1.0.0
typing_extensions==4.12.2