Building Data-Driven Web Apps with Flask and SQLAlchemy Transcripts
Chapter: Routing and URLs
Lecture: Adding a constrained route

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0:00 Now let's go and add
0:01 the rest of the routes to our application here.
0:03 So we've got our home_views
0:04 with index and about.
0:06 I got packages.
0:07 Let's go and create another one of these.
0:08 So we have our blueprint
0:11 for project details.
0:13 But what I want to do is just get the popular ones.
0:16 Now I want to do something really cool with this
0:18 so let's just have this return.
0:21 Details for most popular package.
0:28 It's not going to be exactly perfect
0:29 but now I'm going to pass in a rank
0:33 and it's going to be an integer like so.
0:35 How do we do that in the URL?
0:37 So what I want to do actually is
0:39 I'd like to be able to come over here.
0:41 Is this going to work?
0:42 let me just make a quick change here.
0:47 Now it should run.
0:49 What I want to do is something pretty awesome.
0:52 So if we go over here and we say /about
0:55 we get this. If I say /project/something
0:57 I get something else. But I want to say
1:00 if the thing happens to be a number like 7
1:04 or 5 or 4 or whatever
1:07 I want to run just this function.
1:09 Now if it was
1:11 abc I still want it to do 'not found'.
1:13 But if it's just the number right
1:15 like show me the fifth most popular one
1:18 I would like to pull up that package details.
1:20 I'll give you an example of that as well.
1:21 So if we go over to
1:23 website podcast and you go to the episode
1:26 you can see they have great long URL names
1:28 like /episodes/show/206
1:32 and then a shortened sort of friendly version
1:34 of the title. But sometimes it's nice
1:38 sometimes you just want to share really quickly
1:40 oh like hey that was show 206 like this.
1:44 If you click that and check that out
1:46 it goes right over.
1:48 Want to know what show 205 was?
1:50 There you go, that's what it is.
1:52 So there's this cool way
1:53 to capture only integers.
1:54 There's other stuff that shows up there.
1:56 Like if I go to just /episodes
1:59 that matches but I want to say if it's an integer
2:01 we're going to pull it from the database.
2:03 So let's see that over here.
2:05 And there's a pretty slick way to do this.
2:07 I'm going to go and just say
2:08 we're going to have a /<int:rank>
2:10 and this is going to be a variable.
2:12 So we want to say this
2:13 but only in the case that it's an integer.
2:16 So there's a way to do that in Flask.
2:17 You just say int:rank.
2:21 And now if we go and run this
2:23 and we go I want to go to about
2:25 we get about. But if I want to go to /7
2:28 details for the seventh most popular package.
2:31 /5, fifth most popular package.
2:34 But we can still go to all the rest of our site
2:37 is still working just fine.
2:39 Isn't that cool?
2:40 So anytime you want to have
2:41 some sort of constraint like this
2:43 we can put the type in front and also
2:46 let's just do a real quick print
2:48 type of rank and the value of rank
2:51 real quick there. And let's look again at 11.
2:57 See that Flask already converts that
2:59 to an integer.
3:00 So it's not like working in string
3:02 but it could be an int.
3:03 No it's actually converted to an integer for us
3:06 which is pretty cool. And if it goes abc
3:09 it doesn't match that route
3:10 so it just says 404.
3:11 If we didn't have that integer constraint
3:13 you know potentially that would hit
3:15 and cause a problem right.
3:17 So if we don't have that here for example
3:20 now I can see details for the abc-th.
3:23 That doesn't even make any sense right.
3:25 So we can say only match this short
3:27 sort of Flask / some value
3:30 if it happens to be an integer.
3:31 Really cool we're going to add
3:33 the popular route that way.
3:35 Now the details are not implemented yet
3:36 we'll get to that.
3:37 But a pretty cool way to add
3:39 this specific route here.