Util for making it easier to write decorators

decorators.py

import functools


def kwargs_decorator(decorator):
	""" Allows to easily create docorators with optional keyword argument.
        Decorator must not be called with positional arguments.
        """
	@functools.wraps(decorator)
	def wrapper(wrapped=None, **kwargs):
		if wrapped is None:
                        return lambda f: functools.wraps(f)(decorator(f, **kwargs))
                else:
                        assert callable(wrapped)
			return functools.wraps(wrapped)(decorator(wrapped))
	return wrapper

def smart_decorator(decorator):
	""" Allows to easily create docorators with arguments, without arguments and with optional arguemnts.

	Does not work with decorators that take a single callable argument.
        """
	@functools.wraps(decorator)
	def smart_wrapper(*args, **kwargs):
		if len(args) == 1 and len(kwargs) == 0 and callable(args[0]):
			# single callable argument was passed; assume decorator had no arguments and this is the decorated function
			return functools.wraps(args[0])(decorator(args[0]))
		else:
			# decorator has arguments
			return lambda f: functools.wraps(f)(decorator(f, *args, **kwargs))
			
	return smart_wrapper

example.py

@kwargs_decorator
def log_calls(f, msg='Calling: '):
	def wrapper(*args, **kwargs):
		print "%s %s" % (msg, f.__name__)
		return f(*args, **kwargs) 
	return wrapper

@log_calls
def multiply(a, b):
	return a * b