[MUSIC] 0:00 Hi everyone, I'm Kenneth, your friendly treehouse Django teacher. 0:04 Today, I want to talk to you about a new and 0:08 potentially life-changing feature that's coming to Django named channels. 0:09 As you're already aware, Django provides an incredible framework for 0:13 building Python web applications. 0:16 It has, however, 0:18 long been limited in the kinds of web applications it can support natively. 0:19 Specifically Django has always had trouble supporting more realtime web applications. 0:23 Powered by WebSockets. 0:27 Those kinds of applications have just never been a great fit. 0:28 Until now that is. 0:31 The channel's package provides native WebSocket support Django, and 0:32 his developers make real time WebSockets applications, using the tools and 0:36 ideas there are to use to from Django. 0:39 To understand what channels is doing and why it's such a revolutionary change for 0:42 Django we need to understand a bit more about the technology underneath. 0:45 When you visit a website like teamtreehouse.com our 0:49 computer is being asked by your browser to open a connection to the server 0:52 hosting teamtreehouse.com and then ask for some data. 0:55 The server hosting teamtreehouse.com prepares the data like, 0:59 say the web page for this course and sends it back to your computer. 1:02 Your computer receives the data and 1:05 closes the connection to the server that's hosting teamtreehouse.com. 1:07 I'm glossing over a lot of the specifics because they are required to understand 1:10 web sockets and Django channels, but a handy abstraction, if you're old enough to 1:14 be doing this is calling an airline on the telephone for a flight status update. 1:17 You dial the airline. 1:21 They pick up. 1:22 You request to find information. 1:23 They respond with that information and end the call. 1:24 This one request one response cycle is how websites have operated for 1:27 most of the life of the Internet. 1:30 And the sub Django operates by default. 1:32 The views you write, whether they be function based views or 1:35 class based views, take in a request object and return a response object. 1:37 If you've progressed to the point where you're writing Django middleware 1:41 you might have an even deeper visualization of this in your head 1:44 as you'll know that requests move down the middleware stack. 1:46 And responses move up it until they return to the client requesting the data. 1:49 Django middleware until very recently, specified process request and 1:52 process response functions that made this explicit. 1:56 Given how tightly coupled Django is to the request response cycle, 1:59 channels is even more exciting because web sockets change the underlying structure 2:02 of the request response model. 2:06 Going back to your telephone analogy if the traditional request response model is 2:08 calling up the airline requesting information, getting information back and 2:12 then ending the call WebSockets is calling up the airline, and 2:15 then leaving the line open forever. 2:18 You can ask the airline for information, which they'll give you, but they can also 2:21 let you know when things change, without you asking about those changes each time. 2:23 This is the underlying power of WebSockets. 2:27 The client, in our case the browser, opens a connection to the server, and 2:30 leaves it open. 2:33 The client can pass information to the server. 2:34 Or request information like always, 2:36 but the server can also send information to the client without prompting. 2:38 If you've developed web applications where the data updates regularly, 2:42 you can see what a big idea this is. 2:45 The client can now potentially only load the site once. 2:47 And only load the site's assets. 2:50 The JavaScript, CSS, images, etc., once. 2:51 Once the website connection is opened the server can update the client whenever 2:55 the information changes. 2:58 This ability to keep connections open responding to events and sending messages 3:00 to the connected clients, isn't possible out of the box with vanilla Django. 3:03 Channels works with Django in a very Django way and 3:07 requires fairly minimal code changes for all of the functionality that it's adding. 3:10 Using the channels package and the related tools, Django gains the ability to be 3:14 event driven rather than bound to their request response cycle. 3:17 And as a result can now handle the always connected nature of websites. 3:20 We'll talk more about what channels is going to do for us in the next video, 3:24 where I'll show you the dashboard are we building with channels. 3:27