Convert a decorator into one that allows multiple forms

argumentarize.py

from functools import wraps, partial


def argumentarize(func):
    @wraps(func)
    def decorator(decorated_func=None, /, **kwargs):
        if decorated_func is None:
            # decorator was used with (...)
            # so return the decorator again as partial
            return partial(func, **kwargs)
        if not callable(decorated_func):
            raise TypeError(f"First argument of {func} must be callable. Use keyword arguments instead.")
        return func(decorated_func, **kwargs)

    return decorator


# Usage, apply to a decorator.
# Signature needs to be: deconame(func, /, **kwargs)

@argumentarize
def decorate(func, /, **kwargs):
    @wraps(func)
    def wrapper():
        print("Before", kwargs)
        r = func()
        print("After", kwargs)
        return r

    return wrapper

# Now with that decorator, all three forms are possible:

# regular decorator
@decorate
def foo():
    print('foo')


# decorator called
@decorate()
def bar():
    print('bar')


# decorator called with keyword arguments (no positional possible)
@decorate(foo='bar')
def spam():
    print('spam')


def main():
    foo()
    bar()
    spam()


if __name__ == '__main__':
    main()