Multiple variables (regex groups) on Tornado web application path

Question

I'm switching from Bottle to Tornado. On Bottle I can easily define paths that has multiple variable parts. Like this:

@app.get('/api/applications/<resource>/running_actions/<action_id>')
    def get_application_running_action(resource, action_id):
    # Return running action(<action_id>) of the application (<resource>)

On Tornado I would like to have something like this:

app = tornado.web.Application([
        (r"/api", ApiRootHandler),
        (r"/api/applications/(.*)", ApiApplicationHandler),
        (r"/api/applications/(.*)/running_actions/(.*)", ApiRunningActionsHandler),
        ])

Then ApiRunningActionsHandler would search the application and running actions for the application. But on ApiRunningActionsHandler Get() there is only one path parameter. Is there any way to do this on Tornado or do I just need to parse the path again on ApiRunningActionsHandler? Which actually might not even be possible because I want to direct requests to /api/applications/(.*) to another handler.

Answer 1

I figured it out. Main problem was that my regex was catching everything. So

r"/api/applications/(.*)/running_actions/(.*)" 

actually results only one group. Thus action_id argument wasn't set.

Second issue was that most descriptive path must be defined first.

This works:

class ApiRootHandler(tornado.web.RequestHandler):
    def get(self):
        pass


class ApiApplicationHandler(tornado.web.RequestHandler):
   def get(self, action_name):
       pass


class ApiRunningActionsHandler(tornado.web.RequestHandler):
    def get(self, action_name, action_id):
        self.write("action_name: " + action_name + ", action_id: " + action_id)

app = tornado.web.Application([
    (r"/api/applications/(\w+)/running_actions/([0-9]+)", ApiRunningActionsHandler),
    (r"/api/(\w+)", ApiApplicationHandler),
    (r"/api/", ApiRootHandler),
    ])
app.listen(8888)
tornado.ioloop.IOLoop.current().start()