Decorator that prints the variables in a function (being wrapped) values as they change. Pretty nifty.

log_variables_in_function.py

import sys
from functools import wraps
from typing import Any, Callable, Optional, TypeVar

F = TypeVar("F", bound=Callable[..., Any])

def log_variables(func: F) -> F:
    @wraps(func)
    def wrapper(*args: Any, **kwargs: Any) -> Any:
        def tracer(frame, event, arg) -> Optional[Callable]:
            if event == "return":
                wrapper.locals = frame.f_locals.copy()
            return tracer

        wrapper.tracer = tracer
        sys.settrace(wrapper.tracer)
        try:
            result: Any = func(*args, **kwargs)
        finally:
            sys.settrace(None)

        for name, value in wrapper.locals.items():
            print(f"{name}: {value}")

        return result

    wrapper.locals = {}
    return wrapper