• Able to access request parameters
  
• Does the communication heavy lifting
  
• self.write() to send data to client
  
• self.set_header() set appropriate headers
  
• self.set_status() to modify HTTP status codes
  
• self.redirect() to send user elsewhere

• Can also use templating engine
  
• Python embedded in templates
• Sounds familiar
• Localization is a breeze
• If you use their templates, at least

import tornado.ioloopimport tornado.web
class BaseHandler(tornado.web.RequestHandler):    def get(self):        self.write("Hello, world")application = tornado.web.Application([    (r"/", BaseHandler),])if __name__ == "__main__":    application.listen(8080)    tornado.ioloop.IOLoop.instance.start()

• Easy access to request arguments (GET and POST!)
  
• self.get_argument('name')
  
• ?name=Matt
• arg 'name' required
• only returns last defined argument
• self.get_argument('name', default='John Doe', strip=True)
  
• arg 'name' defaults to 'John Doe', strips whitespace
• self.get_arguments('name') -- return list of arguments 'name'
  
• returns list of argument 'name'
• ?name[]=Matt&name[]=John

class ArgumentHandler(tornado.RequestHandler):   def get(self):      #name is required      name = self.get_argument('name')      names = self.get_arguments('names') # empty list if not present      self.write('Hello, {0}<br />'.format(name))      if len(names) > 0:           self.write('Your list of names are: {0}'.format(                      ', '.join(names)))      else:           self.write("Provide a list of names in the 'names' argument!")

• Registered within Application
  
• Pairs a regular expression with a handler
  
• Regex mapped to handler
  
• Matches provided to handler as parameters
  
• Can map as many Regex to a single Handler as you want
  

application = tornado.web.Application([
    (r"/", MainHandler),    (r"/hello/world/", HelloWorldHandler),    (r"/hello/([^/]+)/?"), HelloAnythingHandler),])