Side Effect Python decorator.

side_effect.py

from functools import wraps


def side_effect(callback, before=True, after=False):
    """A decorator.

    Wraps the decorated function. The callback will be called before and after each
    call of the decorated function according to the parameters.

    Args:
        callback: a function with signature: a_callback(fn, args, kwargs, result=None)
        before: bool
        after: bool
    """
    def decorator(fn):
        @wraps(fn)
        def wrapped(*args, **kwargs):
            before and callback(fn, args, kwargs)
            res = fn(*args, **kwargs)
            after and callback(fn, args, kwargs, result=res)
            return res
        return wrapped
    return decorator