WEBVTT 0 00:00.050 --> 00:03.590 Hey guys, welcome to the final project of today. 1 00:03.590 --> 00:08.930 And in this final project, we're going to be building a Tip Calculator. 2 00:08.930 --> 00:11.750 So the final output is going to look like this. 3 00:11.780 --> 00:12.710 It's going to print, 4 00:12.710 --> 00:14.420 "Welcome to the tip calculator." 5 00:14.420 --> 00:19.490 And it's going to ask you for an input for how much the total bill came to. 6 00:19.520 --> 00:30.740 Let's say that we and a couple of friends went out for lunch, and it came to $124.56, and then it'll 7 00:30.770 --> 00:33.470 ask you, "What percentage tip would you like to give?" 8 00:33.500 --> 00:36.410 So let's say we want to give a 12% tip. 9 00:36.410 --> 00:38.750 So we enter 12 and hit Enter. 10 00:38.780 --> 00:42.560 And then finally it asks, "How many people are splitting this bill?" 11 00:42.560 --> 00:45.800 Let's say there's seven of us and then hit Enter. 12 00:45.830 --> 00:51.530 Finally, it's going to tell us that each person should pay about $19.93. 13 00:51.860 --> 00:58.130 Notice how the final bill, even though after all of these calculations, it's probably got more numbers 14 00:58.130 --> 01:05.690 after the decimal point, we only want two decimal places of accuracy, so it should be rounded to two 15 01:05.690 --> 01:06.890 decimal places. 16 01:06.920 --> 01:14.150 The second thing to remember is that these are percentages, and in order to calculate a percentage 17 01:14.150 --> 01:20.870 of something, you can multiply a number by the percentage number divided by 100. 18 01:21.170 --> 01:26.780 Let me show you this in a little bit more detail, because this project is not about testing your maths, 19 01:26.780 --> 01:30.530 it's about seeing how well you've understood the programming concepts. 20 01:30.560 --> 01:35.570 So let's say that we had a bill of $150. 21 01:35.570 --> 01:45.890 If we were to apply a 12% tip on top of that, then 12% is going to be equal to 12 divided by 100, 22 01:45.920 --> 01:48.710 which is equal to 0.12. 23 01:49.010 --> 01:55.700 Now the next step is we can multiply 150 the total bill by 0.12. 24 01:55.730 --> 02:01.400 And this will give us what 12% of 150 is, which is 18. 25 02:01.460 --> 02:08.170 Now we of course have to add the tip onto the final bill so it becomes 150 + 18. 26 02:08.170 --> 02:13.810 So $150 with 12% tip is equal to $168. 27 02:13.840 --> 02:22.480 Now a shorthand way of doing all of this is simply multiplying 150 by 1.12. 28 02:22.510 --> 02:29.410 So the one is 150, and then it's 0.12 on top of that. 29 02:29.410 --> 02:33.550 So when we do this, it gives us pretty much the same number. 30 02:33.730 --> 02:39.070 Now if during your testing and your coding, you come across some sort of number that looks a little 31 02:39.100 --> 02:45.460 bit strange because you think 150 multiplied by 1.12 should actually equal 168 32 02:45.460 --> 02:46.540 precisely, 33 02:46.540 --> 02:49.780 so what are all of these extra numbers at the end? 34 02:49.810 --> 02:53.050 Now, the short answer is you don't have to worry about it. 35 02:53.050 --> 02:58.690 It's simply related to how Python processes these floating point numbers. 36 02:58.690 --> 03:04.930 If you're really interested and you want to read about this, then I'll link to this page in the Python 37 03:04.930 --> 03:08.380 documentation where they tell you why this is happening, 38 03:08.380 --> 03:11.440 but be warned, it's pretty dense and it's pretty heavy. 39 03:11.440 --> 03:17.650 But the final conclusion is it's just the way that Python is approximating this number, so you don't 40 03:17.680 --> 03:19.420 actually have to worry about this. 41 03:19.450 --> 03:25.150 Now, once we've gotten to 168, the next step is to split it between five people. 42 03:25.150 --> 03:31.810 So, 168 / 5 = 33.6. 43 03:31.840 --> 03:38.080 Now what we want to show the user is we want to show them the amount that they have to pay with two 44 03:38.080 --> 03:39.430 decimal places of accuracy. 45 03:39.460 --> 03:45.190 So we want to say something like 33.60 if this is the case, because that's normally how we represent 46 03:45.220 --> 03:47.710 numbers when it comes to money. 47 03:47.710 --> 03:54.520 So what I want you to do is to also be able to round any of these numbers to two decimal places. 48 03:54.970 --> 04:01.870 If you have successfully created this program, then it should work exactly as this example version 49 04:01.870 --> 04:07.410 would, and you'll be able to see the formatting, where it actually tells you each person should pay 50 04:07.410 --> 04:12.450 this particular dollar amount, and it's rounded to two decimal places. 51 04:12.450 --> 04:19.590 And this is the amount, after taking into consideration these three different inputs from the user. 52 04:19.620 --> 04:25.020 Have a play around with the final product, and then have a think about how you would create this program 53 04:25.020 --> 04:28.500 step by step, and then try to achieve this result. 54 04:28.800 --> 04:34.530 This is going to test everything that you've learned so far, including f-strings, including complex 55 04:34.530 --> 04:41.730 mathematical operations including PEMDAS and calculating numbers, and the order in which mathematical 56 04:41.730 --> 04:47.340 operations are run by a computer, as well as everything you've learned in the previous lessons, and 57 04:47.340 --> 04:48.900 previous days as well. 58 04:48.930 --> 04:53.520 I think this is going to be a lot of fun, and the end result is going to be kind of useful the next 59 04:53.520 --> 04:55.920 time that you need to split the bill between friends. 60 04:55.920 --> 04:58.470 So I'm going to let you pause the video and get on with it. 61 04:58.470 --> 05:03.360 And then once you're done, if you want to, head back over here and I'll walk through the solution with 62 05:03.360 --> 05:08.010 you, but I really recommend you giving it a good go before you come back. 63 05:08.010 --> 05:10.590 So pause the video now and I'll see you later. 64 05:15.780 --> 05:20.760 Okay, so we've seen how the program is supposed to work, and we're trying to create it from scratch 65 05:20.760 --> 05:23.400 by reverse engineering it essentially. 66 05:23.520 --> 05:27.690 Now the first thing our program should say is, "Welcome to the tip calculator!" 67 05:27.690 --> 05:29.490 So that's easy enough. 68 05:29.490 --> 05:31.710 We just have to create a print statement. 69 05:31.740 --> 05:32.580 Perfect. 70 05:32.580 --> 05:38.550 And if you're creating a really enthusiastic tip calculator you can replace the full stop with an exclamation 71 05:38.550 --> 05:39.240 mark. 72 05:39.450 --> 05:44.610 Okay, so let's run it step by step to make sure that we don't have any errors along the way. 73 05:44.610 --> 05:47.370 So the first step seems to be working. 74 05:47.400 --> 05:50.910 Now the next step is to ask the user for some input, 75 05:50.910 --> 05:53.310 and we want to know what was their total bill. 76 05:53.310 --> 05:54.570 Where did it come to? 77 05:54.600 --> 06:00.270 So let's go ahead and create an input and ask them, "What was the total bill?" 78 06:00.300 --> 06:05.910 And then we'll add a dollar sign or whatever currency it is that you prefer to work with 79 06:05.940 --> 06:12.660 because when we actually run this, you'll see that the input will go straight after the end of that 80 06:12.660 --> 06:13.050 string. 81 06:13.050 --> 06:14.820 So, add the dollar sign. 82 06:14.820 --> 06:17.820 So now we can enter a dollar amount like this, 83 06:17.820 --> 06:19.860 but it's not really saved anywhere. 84 06:19.860 --> 06:24.810 This data just disappears because we haven't stored it inside a variable. 85 06:24.810 --> 06:26.400 So let's go ahead and do that. 86 06:26.400 --> 06:28.980 Let's call this variable, bill. 87 06:28.980 --> 06:33.600 And we'll set it to equal whatever the user typed in to this input. 88 06:33.630 --> 06:41.490 Now remember that this bill is going to have a data type of a string. 89 06:41.520 --> 06:41.880 Right? 90 06:41.910 --> 06:48.600 So if I go ahead and hit run and let's just type some numbers in here, you'll see that the data type 91 06:48.600 --> 06:51.390 of the bill is, as we said, a string. 92 06:51.510 --> 06:58.350 In order to be able to do maths, you might remember we have to change this into a number format. 93 06:58.350 --> 07:00.210 So a float or an int. 94 07:00.240 --> 07:05.790 Now in this case, because the bill is likely to have numbers after the decimal place, it's probably 95 07:05.790 --> 07:11.960 better that we turn it into a float so that we get the most accurate result possible. 96 07:12.530 --> 07:19.340 Now that we're done with the bill, the next question the tip calculator should ask is what percentage 97 07:19.340 --> 07:20.720 tip would you like to give, 98 07:20.750 --> 07:22.490 10, 12, or 15? 99 07:22.490 --> 07:26.990 Or you can of course switch this up depending on how much tip you normally give. 100 07:27.050 --> 07:30.770 So the next line is going to be another input. 101 07:32.420 --> 07:36.830 Here I'm asking the user, "How much tip would you like to give?" and giving them some examples. 102 07:36.830 --> 07:43.640 And notice how in my examples, I don't actually have the percentage sign here, because I don't really 103 07:43.640 --> 07:53.150 want them to type the percent sign into this input, because if they do, when they say 12%, this is 104 07:53.150 --> 07:59.870 going to be really hard for me to turn the 12% into an actual number. 105 07:59.870 --> 08:06.080 So you could, in your input message, say something like, "How much tip would you like to give? 106 08:06.260 --> 08:07.520 10, 12 or 15?" 107 08:07.520 --> 08:12.110 Please don't add any percentage signs, just add the number or something like that. 108 08:12.200 --> 08:19.430 But again, once we've done this, it's not stored anywhere unless we add it into a variable. 109 08:19.460 --> 08:24.350 Now we've got a bill that stores the total bill as a float. 110 08:24.350 --> 08:29.750 And we've got a tip which is going to be a whole number, 10, 12 or 15. 111 08:29.780 --> 08:30.290 Right? 112 08:30.290 --> 08:36.590 So depending on what you think is best, you can either turn this into a float or in my case I'm probably 113 08:36.590 --> 08:39.740 going to convert it into an integer. 114 08:39.830 --> 08:45.140 So now we're on to the final step which is how many people to split the bill between. 115 08:45.140 --> 08:48.830 So let's go ahead and create a variable called people. 116 08:48.860 --> 08:57.290 And I'm going to add an int wrapper around this input so that even in the very beginning we know that 117 08:57.290 --> 09:00.590 we have to convert the number of people into a whole number, 118 09:00.590 --> 09:04.820 because I've never had a meal with 3.5 people before. 119 09:05.150 --> 09:09.760 So the input is going to be, "ow many people to split the bill?" 120 09:10.720 --> 09:17.380 And at this point, they should enter the number of people which will turn into an integer stored inside 121 09:17.380 --> 09:19.510 this variable called people. 122 09:19.540 --> 09:25.360 So now that we've got all the data collected from the user, we're finally ready to do some maths. 123 09:25.390 --> 09:35.410 And we said that the way to work out the tip is by multiplying it by 1 point, and then the number 124 09:35.410 --> 09:39.940 after the decimal point is whatever percentage they decided to give. 125 09:39.970 --> 09:46.480 So it would be 1.1 if it was 10% and 1.15 if it was 15%. 126 09:46.540 --> 09:51.610 Let's go ahead and calculate the bill_with_tip. 127 09:52.330 --> 10:00.940 So remember how we said that before the tip percentage is equal to the whole number 10, 12 ,or 15 divided 128 10:00.940 --> 10:06.040 by 100 which turns it into 0.1, 0.12, or 0.15, 129 10:06.070 --> 10:11.260 and then once this calculation is done, we can multiply it by the bill. 130 10:11.710 --> 10:15.850 And then finally we add that to the original bill. 131 10:16.420 --> 10:22.450 So let's go ahead and print this and just check to see that it looks sensible. 132 10:22.450 --> 10:25.900 So bill_with_tip is what we're going to print. 133 10:25.900 --> 10:29.050 And let's put some easy numbers in there. 134 10:29.350 --> 10:34.720 Let's say that the bill was $100 and the tip was 10%, 135 10:34.720 --> 10:38.530 so then the 10% of $100 is $10. 136 10:38.530 --> 10:40.300 So the bill_with_tip, 137 10:40.300 --> 10:44.230 that's what's going to be printed next, it should be 110. 138 10:44.230 --> 10:47.110 So we can type anything in here because we're not using it, 139 10:47.110 --> 10:52.450 and you can see that this calculation, bill_with_tip is 110, which is what we want. 140 10:52.480 --> 10:56.200 Now there's a lot of other ways that you can express this. 141 10:56.200 --> 11:04.630 For example, you could say bill * (1 + tip) / 100). 142 11:04.630 --> 11:08.560 So this would actually give you the same result as well. 143 11:08.560 --> 11:14.950 But remember what we said previously about how Python is a little bit weird with floating point numbers, 144 11:14.950 --> 11:19.510 but essentially this is still giving us the same result, which is 110. 145 11:19.840 --> 11:25.960 So you can choose whichever way you find most intuitive, and if you want, you can even split this 146 11:25.960 --> 11:27.910 up into several steps, right? 147 11:27.940 --> 11:33.550 We could say that tip_as_percent = tip / 100. 148 11:34.300 --> 11:44.500 And then we can multiply the bill by the tip_as_percent to get the total_tip_amount. 149 11:46.420 --> 11:54.280 And then finally we can get the total_bill by adding the bill to the total_tip_amount. 150 11:54.640 --> 12:00.040 Feel free to do this whichever way makes sense to you, but I'm going to leave it with as many steps 151 12:00.040 --> 12:05.260 as possible so that you can actually work through the logic if you got stuck on this maths. 152 12:06.160 --> 12:11.850 Now, the next thing we need to do is to divide the total_bill by the number of people. 153 12:11.850 --> 12:15.540 So if we had five people, then we would divide it five ways, right? 154 12:15.570 --> 12:26.610 So let's call this bill_per_person, which is going to be equal to the total_bill divided by the number 155 12:26.610 --> 12:27.540 of people. 156 12:28.680 --> 12:33.930 Now at this stage, this bill_per_person is a floating point number, 157 12:33.930 --> 12:37.860 so it could have many many digits after the decimal point. 158 12:37.890 --> 12:44.670 If we want to round this to two decimal places, then you might remember from some of the lessons today, 159 12:44.670 --> 12:47.610 we have access to a function called round(), 160 12:47.640 --> 12:53.910 and here we can add the number that we want to round which is the bill_per_person, 161 12:53.910 --> 13:01.230 and then after a comma, we can specify how precise, how many numbers or how many decimal places do we 162 13:01.230 --> 13:02.850 want to round this bill to. 163 13:02.880 --> 13:06.030 And in our case it's two decimal places. 164 13:06.060 --> 13:15.120 So now this is the final amount which I'll call final_amount, which is the bill_per_person rounded 165 13:15.120 --> 13:17.070 to two decimal places. 166 13:17.100 --> 13:25.110 And we can now finally print this to the user and say, "Each person should pay..." 167 13:25.140 --> 13:31.350 And remember, you can either use string concatenation, which will require you to convert this number 168 13:31.350 --> 13:36.810 into a string again, or use the trick that we learned in the previous lessons, where we can create 169 13:36.810 --> 13:44.550 an f-string by adding f in front of the string, and then using some curly braces to insert the {final_amount} 170 13:44.550 --> 13:45.870 right here. 171 13:45.900 --> 13:49.140 And we can write the "{final_amount} dollars..." 172 13:49.140 --> 13:59.250 Or we can put a dollar sign in front and maybe a colon here and now if we clear our console and run 173 13:59.250 --> 14:01.710 our code then you'll see it work. 174 14:01.710 --> 14:03.360 So, "Welcome to the tip calculator! 175 14:03.390 --> 14:04.650 What was the total bill?" 176 14:04.680 --> 14:06.900 Let's make up some random number. 177 14:06.960 --> 14:08.520 "What percentage tip?" 178 14:08.520 --> 14:15.380 Let's say we're going to give 15 and then we're splitting it between five people and it calculates everything, 179 14:15.410 --> 14:17.120 doing all of that maths. 180 14:17.120 --> 14:23.810 And finally, it rounds it to two decimal places, giving us the final amount each person should pay. 181 14:24.500 --> 14:26.780 How did you get on with this project? 182 14:26.780 --> 14:30.590 Did you manage to get it in one go without having to look at the solution? 183 14:30.980 --> 14:36.380 If you got stuck at any point or if your code didn't work as you expect it to, this is the time to 184 14:36.380 --> 14:41.600 go back to it, fix it, and make sure that you've understood everything that's been covered through 185 14:41.600 --> 14:42.770 this exercise. 186 14:43.400 --> 14:48.260 So I hope you had fun building this project and doing all of the coding exercises and learning about 187 14:48.260 --> 14:54.710 mathematical operations, f-Strings, Data Types, Type Conversion, and all of the things that we did 188 14:54.740 --> 14:55.610 today. 189 14:56.000 --> 14:59.090 Have a rest and I'll be back tomorrow 190 14:59.090 --> 15:05.210 teaching you about Conditional Statements, and how we can get the program to do different things depending 191 15:05.210 --> 15:09.560 on certain conditions, or certain parts of our code. 192 15:09.590 --> 15:13.340 So I bid you good night and I'll see you tomorrow.