import datetime
from functools import wraps, partial

def logged(func=None, level="INFO"):
    if func is None:
        return partial(logged, level=level)

    @wraps(func)
    def wrapper(*args, **kwargs):
        print("[%s]: calling %s() %s" % (level, func.__name__, datetime.datetime.now()))
        return func(*args, **kwargs)
    return wrapper

@logged
def now():
    pass

@logged(level="WARN")
def after():
    pass

now()
after()