WEBVTT 0 00:00.140 --> 00:01.430 You've just been hired. 1 00:01.430 --> 00:02.630 Congratulations. 2 00:02.630 --> 00:05.840 But first, there's the matter of coffee. 3 00:05.840 --> 00:10.280 We all know that programmers can't work unless they're loaded up on coffee. 4 00:10.280 --> 00:15.650 So your company has asked you to create the code for a coffee machine. 5 00:16.070 --> 00:22.160 Now, you very cleverly go online and look at the other coffee machines, and you notice that it only 6 00:22.160 --> 00:25.910 costs $230 to buy a coffee machine, 7 00:25.910 --> 00:27.380 but you're not going to cheat, 8 00:27.380 --> 00:29.900 you're going to create everything from scratch. 9 00:29.950 --> 00:34.840 And luckily, we don't actually have to build the hardware because we're programmers, right? 10 00:34.840 --> 00:42.190 But we're going to use this real life coffee machine as the inspiration for our virtual coffee machine, 11 00:42.280 --> 00:45.370 noting the features and the capabilities. 12 00:45.370 --> 00:47.470 So what does it say? 13 00:47.680 --> 00:54.310 I found some wonderful graphics on here, which tells me that there are three hot flavors, which I'm 14 00:54.310 --> 00:56.400 guessing are these three buttons. 15 00:56.400 --> 01:03.750 It's coins operate, which I think they mean it's coin operated, and there's not much else that it 16 01:03.750 --> 01:04.590 can do. 17 01:04.620 --> 01:09.810 Let's take this example and we're going to make a digital version of it. 18 01:09.810 --> 01:12.420 We're going to create our own coffee machine. 19 01:12.420 --> 01:18.030 And the first step we need to replicate is the ability to make three hot flavors. 20 01:18.030 --> 01:24.460 So the flavors we're going to make are one Espresso, two Latte, and three Cappuccino. 21 01:24.550 --> 01:28.480 Here are the recipes for these three types of drinks, 22 01:28.480 --> 01:33.730 each of them requires a different quantity of water, a different quantity of coffee, and a different 23 01:33.730 --> 01:34.990 quantity of milk. 24 01:34.990 --> 01:38.350 And they also each have a different price. 25 01:38.560 --> 01:43.450 We're going to be modeling all this data in our coffee machine program as well. 26 01:43.450 --> 01:49.670 But luckily for you, in the starting code, I've already included all of this data inside a dictionary, 27 01:49.670 --> 01:54.260 so you don't have to remember this, although it might help if you're at home and you decide that you 28 01:54.260 --> 01:57.620 really wanted a latte instead of your usual black coffee. 29 01:57.650 --> 02:02.270 Now, in addition, the coffee machine has some resources that it has to manage. 30 02:02.270 --> 02:09.560 So it starts out with 300 ml of water in the tank, 200 ml of milk, and 100g of coffee. 31 02:09.590 --> 02:14.510 The second feature of our coffee machine is that it's coin operated. 32 02:14.510 --> 02:17.510 So we're going to be using American coins. 33 02:17.510 --> 02:23.330 And they have four types of coins the Penny, the Nickel, the Dime, and the Quarter. 34 02:23.360 --> 02:25.970 They used to also have the Dollar as a coin, 35 02:25.970 --> 02:28.280 but a few years ago they stopped minting that. 36 02:28.280 --> 02:29.300 So we're not going to count it, 37 02:29.300 --> 02:31.940 and it probably means one less if statement for us. 38 02:31.940 --> 02:35.270 Notice what each of these coins are worth. 39 02:35.270 --> 02:41.910 The penny is worth a cent, the nickel worth $0.05, and the dime $0.10, and the quarter is a quarter 40 02:41.910 --> 02:42.720 of a dollar. 41 02:42.750 --> 02:48.210 These represented in decimal values would look something like this. 42 02:48.990 --> 02:50.970 Now here's the important part, 43 02:50.970 --> 02:55.260 let's think about what our program requirements are if we break it down. 44 02:55.680 --> 02:59.580 One we need our coffee machine to be able to print a report. 45 02:59.580 --> 03:05.200 It needs to be able to tell us what resources it has left, how much water has left, how much milk, 46 03:05.200 --> 03:06.070 et cetera. 47 03:06.100 --> 03:11.590 So let's say that we wanted a report on all the resources that the machine has. 48 03:11.620 --> 03:16.960 All we have to do is type report and we can see all the resources we have. 49 03:17.380 --> 03:23.290 Now, in addition to being able to print a report, we also want to be able to check that the resources 50 03:23.290 --> 03:26.410 are sufficient when the user orders a drink. 51 03:26.920 --> 03:30.190 Now let's say that the user decided to order a latte. 52 03:30.520 --> 03:37.270 It asks me to insert some coins and then it gives me the change and it gives me the latte. 53 03:37.300 --> 03:43.480 But now if I check the report, I can see that I've only got 100 ml of water left, 54 03:43.480 --> 03:49.750 and I know from the previous slide that a latte and a cappuccino is going to need more than that amount 55 03:49.750 --> 03:50.560 of water. 56 03:50.570 --> 03:54.710 So let's see what happens if I go ahead and order a cappuccino. 57 03:54.800 --> 03:57.860 It says, "Sorry, there's not enough water." 58 03:57.860 --> 04:05.750 So our program is able to look through all the resources that the machine has, checks it against the 59 04:05.750 --> 04:12.770 recipe of the drink that we're trying to make, and tells the user if there is insufficient water or 60 04:12.770 --> 04:14.300 if there's insufficient milk, 61 04:14.300 --> 04:20.190 and as long as one of the resources is insufficient, then it can't make the drink and it gives the 62 04:20.190 --> 04:21.540 feedback to the user. 63 04:21.960 --> 04:27.930 Now, as you saw before, our program also needs to be able to process coins because our machine is 64 04:27.930 --> 04:33.900 coin operated, so no fancy contactless payment or pay with your Apple Watch, 65 04:33.900 --> 04:34.500 none of that. 66 04:34.500 --> 04:36.120 We've only got coins. 67 04:36.150 --> 04:43.260 When we order something, it should ask us to insert coins, and it's going to ask for the quantity 68 04:43.260 --> 04:44.850 of each type of coin. 69 04:44.850 --> 04:47.940 So let's say that I insert one of each. 70 04:47.940 --> 04:54.540 Then in this case, there's actually not enough money to cover my drink, and it refunds the money and 71 04:54.540 --> 04:55.920 doesn't give me a drink. 72 04:56.010 --> 05:03.480 But on the other hand, if I do insert enough money, then it should be able to calculate how much money 73 05:03.480 --> 05:09.580 all of these coins are worth and then calculate the amount of change based on the cost of my drink, 74 05:09.580 --> 05:13.300 and then it should hand me my drink, and tell me to enjoy. 75 05:13.930 --> 05:19.930 So in addition to being able to process the four types of coins, calculating the actual monetary value 76 05:19.930 --> 05:25.210 based on the number of coins, it should also check that the transaction is successful, that the user 77 05:25.210 --> 05:30.340 didn't try to hoodwink us by not giving enough coins and asking for a drink. 78 05:30.400 --> 05:35.630 So if they haven't inserted enough coins, then we're just going to refund them and tell them, "Sorry, 79 05:35.630 --> 05:38.960 that's not enough money" and not give them their drink. 80 05:38.960 --> 05:44.360 But if the transaction was successful, then we're going to make the coffee, 81 05:44.360 --> 05:49.640 and in the process of making the coffee, we're going to have to deduct the resources. 82 05:49.670 --> 05:54.110 Notice how every time we make a drink say, in this time we made a latte, 83 05:54.500 --> 05:58.530 and previous to the latte we had 300ml of milk. 84 05:58.530 --> 06:04.050 But after the latte, when we asked for the report, you can see that the water has been reduced, the 85 06:04.050 --> 06:08.850 milk has been reduced, the coffee has been reduced, and the money has been put into the coffers. 86 06:09.300 --> 06:15.780 This program, even though it seems simple, just a simple digital version of a coffee machine, it 87 06:15.780 --> 06:18.510 actually has quite a few requirements. 88 06:18.540 --> 06:26.280 Now I've created a detailed program specification for you as a PDF file, which you can download in 89 06:26.280 --> 06:27.810 the Course Resources, 90 06:27.810 --> 06:31.920 and this goes into a lot more details on each of those points. 91 06:31.920 --> 06:39.150 For example, what should the prompt print in the beginning of the program, and then how to turn the 92 06:39.150 --> 06:46.930 machine off, how to print the report, and how each of those points should work in detail. 93 06:46.960 --> 06:53.470 Go ahead and download this and make sure you read each of the sections and test it out in the final 94 06:53.470 --> 06:55.900 working version of the project. 95 06:56.620 --> 07:02.920 Once you're ready, you can go ahead and head over to the starting version of the code, and I want 96 07:02.920 --> 07:08.440 you to create a new project using PyCharm and call it CoffeeMachine. 97 07:10.990 --> 07:21.050 And then create a new file inside your project called main.py, and then paste all of the starting code 98 07:21.050 --> 07:23.180 into your main.py. 99 07:23.180 --> 07:26.120 And now you're going to code inside this file. 100 07:26.120 --> 07:29.210 And once you're ready, you're going to click Run, 101 07:29.210 --> 07:32.750 and you'll be able to run this main.py down here, 102 07:32.750 --> 07:34.970 and this will act as your console. 103 07:35.570 --> 07:41.360 So if I go ahead and take some of these program requirements, I can put them in as TODOs. 104 07:41.360 --> 07:44.810 To create a TODO you have to follow the syntax. 105 07:44.810 --> 07:47.660 First is a pound sign #, 106 07:47.660 --> 07:50.900 and then we write TODO in all caps. 107 07:50.900 --> 07:53.930 And notice how that's just changed color just now. 108 07:53.930 --> 07:58.640 And now you can see in the TODO tab it's found one TODO item. 109 07:58.820 --> 08:02.910 Now we can write TODO Number 1, 110 08:02.910 --> 08:07.920 and this is to print a report of all the coffee machine resources. 111 08:08.550 --> 08:12.420 Now let's say that I created a TODO somewhere else, 112 08:12.420 --> 08:12.750 right? 113 08:12.750 --> 08:14.640 Like all the way up here. 114 08:15.270 --> 08:20.310 "Check that the resources are sufficient to make the drink order." 115 08:20.370 --> 08:24.420 And notice how they're completely in different places, in a different order, 116 08:24.420 --> 08:30.490 but every time I create one of these TODOs using this format, it will get picked up in the TODO tab 117 08:30.490 --> 08:33.370 and you can go ahead and see where they live. 118 08:33.370 --> 08:37.240 So it's found two items inside our main.py. 119 08:37.240 --> 08:39.910 And you can see that this one is TODO: 1. 120 08:39.910 --> 08:41.260 This one is TODO: 2. 121 08:41.260 --> 08:45.460 And when you click on them they'll take you to the correct places in your code. 122 08:46.120 --> 08:52.750 Use this to break down the problem into smaller problems that you can solve one by one, just as you've 123 08:52.750 --> 08:56.890 done before, and try to see if you can complete this project. 124 08:56.920 --> 08:58.480 Just a word of warning. 125 08:58.480 --> 09:04.960 This project is quite ambitious, so give this problem at least an hour to work on it and make sure 126 09:04.960 --> 09:11.890 that you satisfy all the criteria that's set out in the program requirements, and also that your program 127 09:11.890 --> 09:17.260 works exactly the same as the final version of the Coffee Machine.