WEBVTT 0 00:00.290 --> 00:04.400 All right, guys, in this lesson, I have a small coding challenge for you. 1 00:04.430 --> 00:13.490 The goal is to create a Python Pizza Delivery Program, and the program is going to automatically calculate 2 00:13.490 --> 00:18.350 the bill for the user based on a number of options. 3 00:18.350 --> 00:23.120 So the user is going to be asked three questions in the form of an input. 4 00:23.120 --> 00:27.830 And we can run through this program as it is just to see that in action. 5 00:28.010 --> 00:32.260 So firstly it says, "Welcome to Python Pizza Deliveries!" 6 00:32.260 --> 00:34.120 "What size pizza do you want?" 7 00:34.120 --> 00:36.940 And I'm going to choose a large pizza. 8 00:36.940 --> 00:39.700 So it asks me S, M or L? 9 00:39.700 --> 00:43.330 So L. "Do you want pepperoni on your pizza?" 10 00:43.330 --> 00:44.920 Yes, always. 11 00:45.580 --> 00:48.070 And then it asks, "Do you want extra cheese?" 12 00:48.070 --> 00:49.870 I'll type N for no. 13 00:49.870 --> 00:55.410 So these are my inputs which will get saved into these variables: 14 00:55.410 --> 00:58.110 size, pepperoni, and extra_cheese. 15 00:58.200 --> 01:06.180 And what I want to happen is for us to be able to print out the final bill, saying, "Your final bill 16 01:06.180 --> 01:12.900 is..." this amount, and it should be $28 based on the pricing of Python Pizza. 17 01:12.900 --> 01:19.880 So you can see in the description box here we've got all the prices for the Small, Medium, and Large pizzas as 18 01:19.880 --> 01:21.620 well as the modifiers. 19 01:21.620 --> 01:26.270 So if they want pepperoni on a small pizza, that's an extra $2. 20 01:26.270 --> 01:31.580 If they want pepperoni on a medium or large pizza, that's an extra $3. 21 01:31.580 --> 01:36.380 And finally, if they want extra cheese, that's $1 on top of their bill. 22 01:36.950 --> 01:43.880 So your goal is to use what you've learned about if statements, elif statements, else statements, 23 01:43.910 --> 01:45.590 nested if statements, 24 01:45.590 --> 01:47.240 multiple if statements, 25 01:47.240 --> 01:52.730 everything you've learned so far, basically in today's lessons, to be able to build this and get it 26 01:52.730 --> 01:55.760 to do what we expect it to do. 27 01:55.760 --> 02:02.240 So pause the video, have a think about how you might tackle this problem, and work through each of 28 02:02.240 --> 02:04.070 the TODO's in order. 29 02:04.070 --> 02:08.120 Afterwards, come back and we'll go through the solution together. 30 02:08.140 --> 02:11.800 By the way, in this lesson, you can click on the check button, 31 02:11.800 --> 02:18.610 once you think your code is doing what it's supposed to, and we'll run through the automatic test using 32 02:18.610 --> 02:24.790 various options that we've tried for size pepperoni and extra cheese to verify that your code works. 33 02:24.790 --> 02:26.410 So pause the video now. 34 02:36.000 --> 02:38.820 All right, so let's run through the solution together. 35 02:38.820 --> 02:44.340 The first thing we want to do is to work out how much they need to pay based on their size choice. 36 02:44.340 --> 02:46.590 So we've got all the prices here. 37 02:46.590 --> 02:52.410 And we're going to start off with a variable called bill, that's going to start out at zero. 38 02:52.410 --> 02:55.770 And we're going to check the variable size. 39 02:55.770 --> 03:02.630 So if the size that they chose is equal to "S", that means they wanted a small pizza, 40 03:02.630 --> 03:08.180 so then to the bill we will simply add $15. 41 03:08.180 --> 03:11.480 Now at this point, because this is the very first if statement. 42 03:11.480 --> 03:18.200 And we're simply setting the bill depending on the size that they chose, you might have done it differently. 43 03:18.200 --> 03:24.350 You might have done this, you might have said, let's set the bill to equal 15 instead of plus equals. 44 03:24.350 --> 03:28.250 Both of them work and both of them are acceptable solutions. 45 03:28.250 --> 03:34.610 Now I'm going to stick to using the +=, because we're going to be using it a lot in this program. 46 03:34.610 --> 03:40.940 So hopefully you already understand that this is the same as saying plus 15 to the previous value of 47 03:40.940 --> 03:43.760 bill and set it to the new value. 48 03:43.760 --> 03:48.300 So the next thing we need to check is what if they chose a medium sized pizza? 49 03:48.300 --> 03:52.440 So we're going to use elif and we're going to check the second condition. 50 03:52.440 --> 04:00.450 If size that they chose is equal to M, in this case we're going to add $20 to the bill. 51 04:00.450 --> 04:03.960 So we're going to say bill += 20. 52 04:03.960 --> 04:06.090 And the final version, 53 04:06.090 --> 04:12.170 so the L, if they chose a large pizza we need to set it to $25. 54 04:12.170 --> 04:13.970 Now, there's two options here. 55 04:13.970 --> 04:19.010 You might have done an else statement because we've already tackled S and M. 56 04:19.010 --> 04:20.930 The last one is just L. 57 04:20.930 --> 04:27.860 So we could simply set the bill += 25. 58 04:28.100 --> 04:32.180 But you might have also added a another elif statement. 59 04:32.180 --> 04:34.430 So again both of these options work. 60 04:34.430 --> 04:40.370 We can say elif size == "L". Depends on what you want to choose, 61 04:40.370 --> 04:43.700 but both of these options will work just fine. 62 04:44.840 --> 04:50.750 Now you might also want to add a final else statement if you are really careful, 63 04:50.750 --> 04:53.390 because what if they typed something wrong? 64 04:53.390 --> 04:58.490 What if they typed instead of S, M, and L, they typed some mumbo jumbo? 65 04:58.520 --> 05:06.520 Well, that would be tackled in the else statement, and you could print out, "You typed the wrong inputs," 66 05:06.970 --> 05:09.340 just to catch that situation. 67 05:09.370 --> 05:17.530 Now I have a warning sign under my print statement, and it tells me that my indentation is not a multiple 68 05:17.530 --> 05:18.160 of four. 69 05:18.160 --> 05:23.710 So just in case this happens to you, just make sure that every time you use an indent that you've got 70 05:23.710 --> 05:25.480 four spaces in there. 71 05:25.480 --> 05:31.710 So if I just add one more space and make sure that all of these are on the same indentation line, that 72 05:31.710 --> 05:32.910 warning goes away. 73 05:32.910 --> 05:34.950 So we're done with the first to do. 74 05:34.980 --> 05:39.390 We've worked out how much to add to the build based on the user's size choice. 75 05:39.390 --> 05:43.380 The next thing to do is to figure out if they chose any pepperoni. 76 05:43.380 --> 05:50.600 So if pepperoni is equal to Y, then in that case we need to add some money to their bill. 77 05:50.600 --> 05:51.950 But how much? 78 05:51.980 --> 05:55.880 Well, it depends on the size of their previous choice. 79 05:55.880 --> 05:59.540 So if they had a small pizza, it's $2. 80 05:59.540 --> 06:02.060 And if they had a large pizza it's $3. 81 06:02.060 --> 06:05.960 So the easiest way to do this is to use a nested if statement. 82 06:06.500 --> 06:12.860 So inside the previous if statement, we've already checked to make sure that they chose Y for pepperoni. 83 06:12.860 --> 06:18.910 So yes to pepperoni if we add another if statement here, this will only be checked if they already 84 06:18.910 --> 06:20.560 said they wanted pepperoni. 85 06:20.560 --> 06:28.570 So if the size is equal to S, then this is the case of a pepperoni on a small sized pizza. 86 06:28.570 --> 06:33.760 So to the bill we can add $2 now. Else, 87 06:33.760 --> 06:37.450 so they chose, "Yes" to pepperoni, but they have a different size. 88 06:37.450 --> 06:46.830 Then we can say the bill should add equal $3, and that solves the pepperoni problem with a nested if 89 06:46.830 --> 06:49.950 statement inside another if statement. 90 06:50.190 --> 06:56.070 So the final to do is to work out their final amount based on whether if they want extra cheese. 91 06:56.070 --> 07:01.290 So this is a situation where we have multiple if statements. 92 07:01.290 --> 07:03.630 So we have an if statement here that's being checked. 93 07:03.630 --> 07:06.140 We have an if statement here that's being checked. 94 07:06.140 --> 07:10.520 And finally we have an if statement that checks if they want extra cheese. 95 07:10.520 --> 07:20.810 So if this is equal to yes, then all we need to do is, add the $1 to the bill. 96 07:20.810 --> 07:26.750 And that is all we need to do to complete this last, addition. 97 07:26.750 --> 07:38.030 And now we can finally print out the value where we say, "Your final bill is..." and then colon, and then 98 07:38.030 --> 07:39.080 a dollar sign. 99 07:39.080 --> 07:45.740 And then we're going to use an f-string to insert the amount for our bill right here. 100 07:45.740 --> 07:49.490 And finally we need a full stop. 101 07:49.520 --> 07:56.200 Now make sure that you've actually got everything written exactly as I have, because otherwise the 102 07:56.200 --> 07:58.150 checks are not going to pass. 103 07:58.150 --> 08:06.490 So now that I've made sure I've got all the right full stops and, all the right wording, and hopefully 104 08:06.490 --> 08:13.090 my calculations are correct, I can now click on check and if everything is correct then it tells me 105 08:13.090 --> 08:15.250 congratulations, everything's correct. 106 08:15.910 --> 08:20.440 So hopefully that wasn't too hard and you managed to figure it out by yourself. 107 08:20.440 --> 08:26.380 If not, this is the time to go back and fix your code based on what you've learned in the solutions. 108 08:26.380 --> 08:29.710 We all make mistakes and we all need help to figure out things. 109 08:29.710 --> 08:33.880 There's nothing wrong with learning from the solution. 110 08:33.880 --> 08:34.720 Walkthrough. 111 08:34.720 --> 08:37.570 As long as you understand everything that's going on. 112 08:37.570 --> 08:39.850 So go ahead and do that if you need to. 113 08:39.850 --> 08:44.200 Otherwise, head over to the next lesson where we're going to learn about logical operators.