My implementation of Python decorators based on functions (not class-based decorator).

function_decorator.py

def login_required(function=None, message=None):
    """
    Decorator for views that checks that the user is logged in,
    or show error page with message.

    >>> We can use any of this forms of decorator:
    >>>
    >>> # 1. without parameters
    >>> @login_required
    >>> def my_function(request):
    >>>     pass
    >>>
    >>> # 2. with parameters
    >>> @login_required(message='This page available only for logged in users')
    >>> def my_function(request):
    >>>     pass

    @url https://github.com/1st/django-startup/
    @author Anton Danilchenko <anton.danilchenko@me.com>
    """
    def real_decorator(func):
        def _wrapper(request, *args, **kwargs):
            if request.user.is_authenticated():
                return func(request, *args, **kwargs)
            raise Http404(message)
        return _wrapper

    if function:
        return real_decorator(function)
    return real_decorator