#100DaysOfCode in Python Transcripts
Chapter: Days 88-90: Home Inventory App
Lecture: Bug and functionality fixes

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0:00 So while the app actually does work
0:03 there are quite a few things that we've left out.
0:05 And I've done this on purpose because this is what I'd
0:08 like you to work on for your Day 3.
0:11 If not, just work on to expanded just for fun.
0:14 You can do it after your 100 days is up,
0:15 whatever you feel like.
0:17 Or maybe you can use it as an idea
0:19 to factor it into your own inventory app.
0:22 This first thing is,
0:24 is that we haven't actually captured incorrect input.
0:29 We have here.
0:30 So for example, if we're at the main menu
0:32 we put the letter a.
0:34 We just get invalid option, try again.
0:37 Even if we do something like 11.
0:39 We know it's a number but it doesn't
0:41 match any of these, so we get invalid option try again.
0:45 Now what happens if we add a room?
0:48 Now we know we have kitchen in there.
0:50 But if we add kitchen again, what happens?
0:54 Kitchen already exists.
0:56 So we need to be able to capture that.
0:58 What happens if someone wants to add multiple bedrooms
1:02 but they just want to call it bedroom.
1:05 It's a silly scenario because can't think of anyone who'd
1:08 do that but this is something that needs to be captured.
1:11 Rather than allowing an error to just suddenly pop up
1:14 and then exit out of the app.
1:17 So there's one.
1:19 Adding multiple rooms can cause a problem.
1:22 So, see if you can figure out a way to capture that.
1:26 Now that we have that,
1:29 let's see if we can add duplicate items.
1:32 So we'll add a knife for $20.
1:38 Let's try and add another knife for $20.
1:41 And that works.
1:42 So why does that work?
1:43 Well that actually works because SQLite has its own
1:47 sort of tagging behind the scenes.
1:49 It tags each entry with its own id.
1:53 So you can have duplicates items below a table name.
1:58 You can't have duplicate table names though.
2:01 Now is that a problem?
2:02 For me i don't think it is a problem.
2:04 But if you wanted to capture that you could.
2:07 That's something to capture.
2:09 But what about this?
2:12 Let's say we want to add a microwave,
2:17 but by accident instead of hitting $20 we hit 2o.
2:24 We've entered in a letter instead of a number.
2:29 What's going to happen?
2:30 It allowed it didn't it?
2:31 So it allowed the fact that we had a letter and a
2:35 number in there.
2:36 Which is wrong,
2:38 so if you actually pull up our
2:40 SQLite database in SQLite viewer.
2:42 Which I have done here.
2:44 You can see we now have values
2:48 but microwave is now accepted to O.
2:53 So what we'll do now
2:55 by allowing this to happen,
2:57 we've probably caused problems here.
2:59 So view inventory list, let's do kitchen.
3:04 There we go, it failed because
3:06 it needs it formatted as a number not a string.
3:11 This is for the actual value calculation.
3:15 So it was able to print it all out.
3:17 Once it got to the actual calculation for the total value,
3:21 didn't like it.
3:22 Same thing for actually printing out
3:24 microwave and its value.
3:27 So that's something we screwed up and we'd actually,
3:29 in that case we actually broken the application completely
3:33 because we have no way in here to code a deletion.
3:36 Which again is something you could do.
3:38 So I'm going to go manually into the database here.
3:42 And we'll delete this record
3:47 because it's going to cause us problems.
3:50 I'll demonstrate that again.
3:51 This time we'll add an item to the inventory.
3:54 We'll choose the room study.
3:58 Study.
3:59 And then let's add ourselves a chair.
4:02 And instead of actually entering a number at all.
4:05 Let's just use the word water.
4:07 And you can see it actually returned
4:09 and we were able to add it successfully to the table.
4:11 So again, that's going to cause us issues
4:14 and we'll have to delete it manually from the database.
4:17 We can also capture different errors to do with launching
4:20 the app as we saw.
4:22 I've only got this sampler here but we can actually put
4:24 some more scenarios in there if you wanted.
4:28 That's something you could work on.
4:30 And the last thing here is, check this out.
4:35 We just entered an empty room.
4:38 A room with name space has been added to the database.
4:43 That's a problem, so.
4:45 That's something we need to capture as well.
4:48 This is all stuff you can work towards.
4:50 If you get bored and if you want to work towards it.
4:52 But you can see that this is all stuff,
4:55 if you're creating an app that you have to take
4:58 into account.
4:59 And just one other thing as well that is rubbing me
5:02 the wrong way.
5:03 Is this elif tree here.
5:06 I don't like that, I've done it
5:08 just for demonstration purposes but essentially
5:11 you would preferably throw all of these into a dictionary
5:16 and make it a bit more Pythonic.
5:19 There's no need for it to be this large.
5:21 But either way, this is your little go to points to
5:24 see if you can expand on this and improve it.
5:27 If you wish.
5:28 You might even just think about writing this app
5:30 yourself in a way that you see fit.
5:33 And covering these problems as you build it.
5:37 So have fun.