Python Jumpstart by Building 10 Apps Transcripts
Chapter: App 10: Movie Search App
Lecture: Introduction to the movie search app
0:00 Application number 10, let's build a movie search app.
0:03 Now it turns out we are going to put this movie search app
0:06 into a particularly unreliable environment,
0:10 so we are going to have to do a lot of work
0:12 to make sure our movie search app is durable
0:15 and it doesn't crash or behave too weirdly.
0:18 Let's see how that's going to go.
0:20 We are going to build an app that looks like this, standard header.
0:22 We are going to enter some text and this text is going to be the title of a movie.
0:27 So, here we might say Top Gun,
0:30 and we'll try to go out to the internet and find information
0:33 about movies with Top Gun in their title,
0:35 but you can see in this case it said oh sorry,
0:37 the network happens to be down so no searching right now.
0:41 But our app doesn't crash or give weird errors it just says hey, the network is down,
0:45 check your wi-fi or something like this.
0:47 Then later we try again, search for Top Gun and boom,
0:49 we get real live movie search results off the internet.
0:53 So it might sound like this is about searching movies,
0:56 but really what we are going to focus on is error handling,
0:59 writing durable reliable applications.
1:02 So we are going to focus on error handling,
1:05 the primary way to do this in Python is with exceptions, and try/except blocks,
1:10 you'll see that we can have
1:12 multiple sort of error handling clauses in any particular situations,
1:17 so there might be a host of reasons that our movie app doesn't work,
1:21 maybe the DNS server is down, maybe we entered a bad title,
1:26 maybe the wi-fi is down, maybe the other server actually gave a 500,
1:30 maybe malformed data came back,
1:32 so we can actually catch different errors and give different messages back.
1:37 We might want to tell the users something different
1:39 if the data that came back was malformed,
1:42 rather than if the network was not connected.
1:45 Right, so we'll use multiple what are called except blocks to do this
1:48 and that will allow us to differentiate errors based on the type of the error,
1:52 and ultimately, we are going to talk about writing reliable code
1:56 and you also see how to raise errors and exceptions
1:59 not just catch them because we are going to throw some
2:02 to sort of make our app particularly unreliable.