1 00:00:01,020 --> 00:00:02,130 In this exercise, 2 00:00:02,130 --> 00:00:03,510 we're going to write some code 3 00:00:03,510 --> 00:00:08,280 to upgrade the previous version of our BMI calculator. 4 00:00:08,280 --> 00:00:12,570 So this is our BMI calculator 2.0, if you will. 5 00:00:12,570 --> 00:00:14,250 Now, we're going to write a program 6 00:00:14,250 --> 00:00:17,280 that interprets the Body Mass Index 7 00:00:17,280 --> 00:00:20,280 instead of just simply printing out what it is, 8 00:00:20,280 --> 00:00:21,450 because for most people, 9 00:00:21,450 --> 00:00:23,730 these numbers don't really mean anything. 10 00:00:23,730 --> 00:00:25,530 If you take a look in the description pane, 11 00:00:25,530 --> 00:00:27,870 you'll see that there is a chart 12 00:00:27,870 --> 00:00:32,870 that shows how different BMI are classified by doctors. 13 00:00:33,330 --> 00:00:35,340 If you are within the green band, 14 00:00:35,340 --> 00:00:39,270 so if your BMI is between 18.5 and 25, 15 00:00:39,270 --> 00:00:42,930 then that is considered the normal weight. 16 00:00:42,930 --> 00:00:45,180 And depending on which band you are in, 17 00:00:45,180 --> 00:00:47,460 then there are different classifications 18 00:00:47,460 --> 00:00:49,650 that doctors have come up with. 19 00:00:49,650 --> 00:00:50,820 What we're going to do 20 00:00:50,820 --> 00:00:53,910 is we're going to take a user's height and weight, 21 00:00:53,910 --> 00:00:55,740 we're going to calculate the BMI, 22 00:00:55,740 --> 00:00:58,080 and we're going to output a print statement 23 00:00:58,080 --> 00:01:03,080 telling them, "Your BMI is X...", whatever it is we calculated, 24 00:01:03,210 --> 00:01:07,140 and then we're going to give them an interpretation. 25 00:01:07,140 --> 00:01:10,740 You are underweight or you have a normal weight, 26 00:01:10,740 --> 00:01:13,290 and you can check in the description pane 27 00:01:13,290 --> 00:01:16,980 for exactly what your output needs to match. 28 00:01:16,980 --> 00:01:18,930 Now, I know people are a little bit sensitive 29 00:01:18,930 --> 00:01:22,620 about these topics, and there are certain statements, 30 00:01:22,620 --> 00:01:26,100 like you are obese or you are slightly overweight, 31 00:01:26,100 --> 00:01:28,020 that can be difficult, 32 00:01:28,020 --> 00:01:31,800 but just know that these are words that have come 33 00:01:31,800 --> 00:01:36,420 from the clinical interpretations of the BMI 34 00:01:36,420 --> 00:01:41,010 and we are just going to output them from our calculator. 35 00:01:41,010 --> 00:01:43,290 Take a look at some of the Example Inputs 36 00:01:43,290 --> 00:01:46,050 and Example Outputs and see what it is 37 00:01:46,050 --> 00:01:49,230 that you are expected to create. 38 00:01:49,230 --> 00:01:51,810 And then see if you can remember 39 00:01:51,810 --> 00:01:55,890 how to create the BMI calculator second time round 40 00:01:55,890 --> 00:01:59,010 and add in a slight interpretation 41 00:01:59,010 --> 00:02:01,620 like the ones you see in the description pane. 42 00:02:01,620 --> 00:02:03,993 Have a go at this coding exercise. 43 00:02:12,650 --> 00:02:14,940 So the first step is to do what we did before, 44 00:02:14,940 --> 00:02:18,150 which is to calculate the BMI using the formula 45 00:02:18,150 --> 00:02:21,600 of weight divided by height squared. 46 00:02:21,600 --> 00:02:24,540 And once we've gotten hold of that value, 47 00:02:24,540 --> 00:02:27,540 then we can use our if and else statements 48 00:02:27,540 --> 00:02:30,513 to figure out which interpretation we should give them. 49 00:02:31,410 --> 00:02:36,410 In the case where their BMI is less than 18.5, 50 00:02:36,510 --> 00:02:41,510 then we should print out, "Your BMI is..." whatever it is, 51 00:02:42,030 --> 00:02:44,940 and then "you are underweight." 52 00:02:44,940 --> 00:02:47,400 And this condition is checked 53 00:02:47,400 --> 00:02:50,043 in the first if statement on line 5. 54 00:02:51,120 --> 00:02:53,670 Now, because there are many conditions, 55 00:02:53,670 --> 00:02:55,770 not just a single one, 56 00:02:55,770 --> 00:02:59,220 we're going to need to use the "elif statement". 57 00:02:59,220 --> 00:03:03,330 So we write elif, which stands for else if, 58 00:03:03,330 --> 00:03:06,300 and we can provide another condition to check. 59 00:03:06,300 --> 00:03:10,290 Well, if the BMI is not less than 18.5, 60 00:03:10,290 --> 00:03:12,150 we go on to line 7. 61 00:03:12,150 --> 00:03:15,420 elif is the BMI less than 25. 62 00:03:15,420 --> 00:03:19,290 So that means if the first statement on line 5 was false, 63 00:03:19,290 --> 00:03:21,870 then line 7 actually checks to see 64 00:03:21,870 --> 00:03:26,220 if the BMI is between 18.5 and 25. 65 00:03:26,220 --> 00:03:29,010 And when the BMI is within that range, 66 00:03:29,010 --> 00:03:32,970 then the print statement, "Your BMI is X, 67 00:03:32,970 --> 00:03:36,033 you have a normal weight." will be printed out. 68 00:03:37,170 --> 00:03:40,350 Next, we have two further elif statements 69 00:03:40,350 --> 00:03:43,920 to check if their BMI is between 25 and 30 70 00:03:43,920 --> 00:03:46,830 and also between 30 and 35, 71 00:03:46,830 --> 00:03:50,403 and we print out the corresponding interpretation. 72 00:03:51,750 --> 00:03:55,980 Finally, we cap off our conditional statement with an else 73 00:03:55,980 --> 00:03:59,040 which covers all the other situations. 74 00:03:59,040 --> 00:04:01,710 And in this case, because we've been pretty granular 75 00:04:01,710 --> 00:04:03,540 with our different conditions, 76 00:04:03,540 --> 00:04:04,740 the only other condition 77 00:04:04,740 --> 00:04:07,020 that's going to trigger the else statement 78 00:04:07,020 --> 00:04:10,950 is if the BMI is 35 or over. 79 00:04:10,950 --> 00:04:14,220 And in this case, we give them the final interpretation 80 00:04:14,220 --> 00:04:16,470 inside this print statement. 81 00:04:16,470 --> 00:04:19,380 If you had any issues with getting the code 82 00:04:19,380 --> 00:04:22,530 to pass the tests in the previous slide, 83 00:04:22,530 --> 00:04:25,710 then see if you can understand 84 00:04:25,710 --> 00:04:28,170 what's going on in this code solution 85 00:04:28,170 --> 00:04:30,813 and try to fix your code as needed.