Flask+AppEngine user decorator

gistfile1.py

"""
Decorator that retrieves the current user from app engine and sets it on the wrapped function

Usage:
@user
[function definition]

or
@user("userobj")
def func(userobj, bar, baz)
"""
def user(func = None, var = "user"):
	assert func is None or hasattr(func, '__call__')
		
	def decorator(func):
		@wraps(func)
		def inject_user(*args, **kwargs):
			user = users.get_current_user()
			if not user:
				return redirect(users.create_login_url(request.url))

			argspec = inspect.getargspec(func)
			nkwargs = kwargs.copy()
			nargs = list(args)

			if var in argspec.args: # user is an arg
				if argspec.args.index(var) is not 0:
					raise AssertionError("{} should be the first function argument".format(var))
				nargs.insert(0, user)
			elif argspec.keywords is not None: # varargs -> set it
				nkwargs[var] = user
			else:
				raise AssertionError("user argument not found, make sure decorated function has {} as argument (or has **kwargs)".format(var))
			return func(*nargs, **nkwargs)

		return inject_user

	if func != None:
		return decorator(func)
	else:
		return decorator

Hacky :(