python decorator trick (can have options or not)

decorator.py

def fb_session_required(arg1=True):
    verify = arg1 is True
    def decorate(f):
        @wraps(f)
        def check(*args, **kwargs):
            if not request.values.has_key('fb_sig_session_key'):
                return "Requires facebook session", 403
            if verify and get_access_token(use_cache=False):
                return "Requires valid facebook session", 403
            return f(*args, **kwargs)
        return check
    return verify and decorate or decorate(arg1)


@app.route('/session_required')
@fb_session_required
def session_required():
    return 'facebook session exists'

@app.route('/valid_session_required')
@fb_session_required(True)
def valid_session_required():
    return 'valid facebook session exists'