1 00:00:00,750 --> 00:00:03,060 All right. So in today's coding challenge, 2 00:00:03,090 --> 00:00:05,250 we're going to do a little bit of wall painting. 3 00:00:05,850 --> 00:00:10,850 And the idea is we're going to create a program that helps us calculate how many 4 00:00:11,220 --> 00:00:16,220 cans of paint we need to buy for a given surface area of wall. 5 00:00:17,220 --> 00:00:19,320 The maths involved is very simple 6 00:00:19,350 --> 00:00:22,110 and I'm going to talk you through it if you're not confident with maths. 7 00:00:22,500 --> 00:00:26,370 But essentially we want it to be able to use our inputs 8 00:00:26,640 --> 00:00:31,380 to modify our function so that it does something every single time we use it. 9 00:00:32,430 --> 00:00:37,410 Go ahead and click on day 8.1 area calculation, 10 00:00:38,040 --> 00:00:42,510 and we're going to complete this coding challenge. So firstly, 11 00:00:42,510 --> 00:00:46,290 you'll notice that down here on lines, 10, 11, 12, and 13, 12 00:00:46,710 --> 00:00:50,160 I've got some code that's going to help us check your solution. 13 00:00:50,700 --> 00:00:55,700 And we're going to use your function to actually calculate the number of cans of 14 00:00:56,820 --> 00:00:57,810 paint we need to buy. 15 00:00:58,470 --> 00:01:02,970 You're basically painting a wall and the instructions on the paint cans says that 16 00:01:02,970 --> 00:01:03,803 one can 17 00:01:04,110 --> 00:01:09,110 can cover five square meters of wall. Given any height and any width, your 18 00:01:10,500 --> 00:01:15,360 program needs to calculate how many cans of paint you need to buy. The maths, 19 00:01:15,570 --> 00:01:17,040 as I say, is pretty simple. 20 00:01:17,070 --> 00:01:21,150 All you have to do is multiply the height by the width to get the area of the 21 00:01:21,150 --> 00:01:25,290 wall, and then you simply divided by the coverage per can. 22 00:01:25,860 --> 00:01:28,340 We said that five square meters per can, so 23 00:01:28,350 --> 00:01:30,750 it means you are always going to be dividing by five. 24 00:01:31,230 --> 00:01:35,250 So let's say that we had a wall which was two meters high and four meters wide, 25 00:01:35,700 --> 00:01:39,150 and the coverage, as always, is going to be equal to five. 26 00:01:40,020 --> 00:01:43,800 Then the calculation would be a simple as 2 x 4 divided by 5, 27 00:01:43,830 --> 00:01:48,210 which is 1.6. So we need 1.6 cans of paint, 28 00:01:48,540 --> 00:01:52,050 but because you can't buy 0.6 can of a paint, 29 00:01:52,470 --> 00:01:56,460 I've tried this in the store. They said no and they told me to go away. 30 00:01:57,300 --> 00:02:02,300 So we actually have to round up to the nearest whole number. 31 00:02:03,240 --> 00:02:06,870 So in this case, we need to buy two cans. Now, 32 00:02:06,900 --> 00:02:10,830 the really important thing to draw your attention to is down here 33 00:02:10,860 --> 00:02:13,350 I actually call the function. 34 00:02:13,770 --> 00:02:18,750 So I'm calling the function and I'm giving in some named arguments. 35 00:02:19,080 --> 00:02:23,520 So this is really, really important. If you review the previous lessons, 36 00:02:23,580 --> 00:02:27,870 then you should know what name you need to give your function and what 37 00:02:27,870 --> 00:02:32,870 name you need to give the parameters for the code to actually work without any 38 00:02:32,970 --> 00:02:37,950 errors. Remember to take a look at the example inputs down here 39 00:02:37,980 --> 00:02:42,980 and example output because you need to print out something along these lines. 40 00:02:43,650 --> 00:02:48,300 So it should say you'll need X cans of paint depending on your calculation. 41 00:02:48,870 --> 00:02:52,920 And finally, if you need a hint as to how to round up a number, 42 00:02:53,250 --> 00:02:57,180 then you can either go ahead and Google for it, use Stack Overflow, 43 00:02:57,240 --> 00:03:01,540 that's probably the best way, or you could give it a guess. And finally, 44 00:03:01,540 --> 00:03:02,680 if you really get stuck, 45 00:03:02,710 --> 00:03:06,640 take a look at the hint section. And once you're done, 46 00:03:06,700 --> 00:03:10,060 then come back over here and we'll walk through the solution together. 47 00:03:10,600 --> 00:03:14,080 Pause the video now and go ahead and complete this coding exercise. 48 00:03:21,750 --> 00:03:22,380 Yeah. 49 00:03:22,380 --> 00:03:25,560 All right. So, did you manage to get that right? If not, 50 00:03:25,710 --> 00:03:28,410 take a look at this video and then once you're done, 51 00:03:28,620 --> 00:03:33,090 take a look at the solution code and try to compare against your code to see if 52 00:03:33,090 --> 00:03:37,110 there were any errors that you made. Now, this challenge is pretty doable. 53 00:03:37,470 --> 00:03:42,470 All we have to do is to create our function and we create any function using def. 54 00:03:43,500 --> 00:03:46,830 And how do we know what name to give this function? Well, 55 00:03:46,830 --> 00:03:49,950 we take a look at where the function was called down here, 56 00:03:50,520 --> 00:03:53,850 and you can see that it's called paint_calc. 57 00:03:54,240 --> 00:03:56,910 So this is what we have to give our function as the name. 58 00:03:57,630 --> 00:04:02,370 And then we of course have our parentheses, our colon, and then inside here, 59 00:04:02,400 --> 00:04:04,920 we're going to do all the calculations. Now, 60 00:04:04,920 --> 00:04:09,030 the next thing we have to look at is what name we should give our parameters. 61 00:04:09,510 --> 00:04:12,540 And you can see I've got named arguments here. 62 00:04:12,930 --> 00:04:17,820 So that means each of these are going to be the names of the parameters; height, 63 00:04:18,300 --> 00:04:19,950 width, and cover. 64 00:04:20,460 --> 00:04:25,460 So the parameters are going to go inside the parentheses height, width, and cover. 65 00:04:27,060 --> 00:04:31,620 And it's only if we actually spell these parameters exactly the same as what we've 66 00:04:31,620 --> 00:04:35,280 got down here in the arguments will our code actually work. 67 00:04:36,780 --> 00:04:41,160 Now let's go ahead and take the height and multiply it by the width to get the 68 00:04:41,160 --> 00:04:45,240 area. So area = height * width. 69 00:04:46,440 --> 00:04:50,460 And then with that area, we can divide it by the coverage per can. 70 00:04:50,520 --> 00:04:55,520 So let's call it num_of_cans = area 71 00:04:55,890 --> 00:04:57,720 / cover. 72 00:05:00,000 --> 00:05:04,560 And now remember that this is going to be a decimal number occasionally like 73 00:05:04,560 --> 00:05:05,393 here, 74 00:05:05,520 --> 00:05:09,780 and we have two round it up to the next whole number. 75 00:05:10,410 --> 00:05:14,370 If we take a look at this particular Stack Overflow, 76 00:05:15,480 --> 00:05:18,540 you can see that the question is exactly what we want, right? 77 00:05:18,540 --> 00:05:22,620 How do you round up a number in Python? And if you did some Googling, 78 00:05:22,620 --> 00:05:26,730 then this might have been the Stack Overflow question you would have landed on. 79 00:05:27,360 --> 00:05:32,220 And essentially it tells us you have to import maths, and from the math module, 80 00:05:32,230 --> 00:05:36,180 you use a function called ceiling. And then inside the parentheses, 81 00:05:36,270 --> 00:05:39,390 you put in the inputs. To do that, 82 00:05:39,420 --> 00:05:41,280 we first import math. 83 00:05:42,690 --> 00:05:47,690 It's math without the 's.' And then we can call it a math.ceil and wrap this 84 00:05:50,130 --> 00:05:52,110 result around the parentheses. 85 00:05:52,410 --> 00:05:56,250 So this is going to take the result here from a decimal number to 86 00:05:56,250 --> 00:05:59,510 a whole number by rounding it up to the ceiling. 87 00:06:00,260 --> 00:06:03,380 So now we're finally ready to give our output, 88 00:06:03,410 --> 00:06:05,660 so we're going to do that by printing it. 89 00:06:05,660 --> 00:06:09,560 So we're going to print and I'm definitely going to need an f-string. 90 00:06:09,560 --> 00:06:13,040 So I'm going to put an F in there and paste this string. 91 00:06:13,340 --> 00:06:16,430 And instead of having the hard-coded five here, 92 00:06:16,940 --> 00:06:20,630 I'm going to put in the num_of_cans instead. 93 00:06:21,500 --> 00:06:26,500 So now when this line of code on line 17 calls 94 00:06:27,050 --> 00:06:31,310 paint_calc passing in each of these arguments, 95 00:06:32,210 --> 00:06:37,210 then it's going to be able to run this function here and print out how many cans 96 00:06:38,180 --> 00:06:42,830 of paint I'll need. Now, all we have to do is test our code. 97 00:06:43,010 --> 00:06:46,490 So let's hit run and let's put in a random height. 98 00:06:46,490 --> 00:06:50,930 Let's say it's five meters high and three meters wide. 99 00:06:51,560 --> 00:06:54,050 And it tells us that we need three cans of paint. 100 00:06:54,560 --> 00:06:57,890 So five by three, 101 00:06:57,890 --> 00:06:59,750 the area is 15 square meters, 102 00:07:00,140 --> 00:07:03,860 15 divided by five is three. Now, 103 00:07:03,860 --> 00:07:05,960 what if we had a decimal number? 104 00:07:06,290 --> 00:07:10,430 Let's say we had a height of 7 and a width of 13. 105 00:07:11,180 --> 00:07:14,060 Then in this case, it tells us we need 19 cans. 106 00:07:14,120 --> 00:07:19,120 So 7 times 13 is 91. 91 divided by 5 is 18.2 and 18.2 107 00:07:22,010 --> 00:07:23,900 round it up is 19. 108 00:07:24,680 --> 00:07:29,330 And we've now completed this challenge. Did you manage to get it right? 109 00:07:29,660 --> 00:07:34,660 If not, be sure to watch this video and see if you can go back and fix your code 110 00:07:35,150 --> 00:07:39,560 and you can compare it against the solution code I've got here by going to this 111 00:07:39,590 --> 00:07:40,580 link right here. 112 00:07:42,260 --> 00:07:46,220 And once you're done, head over to the next lesson where I've got a slightly 113 00:07:46,220 --> 00:07:48,170 harder coding challenge for you.