1 00:00:04,460 --> 00:00:10,100 So let's look at simplifying chained comparisons. The code on line 3, 2 00:00:10,100 --> 00:00:14,090 if you check carefully, is underlined with s squiggly line, which intellij and 3 00:00:14,090 --> 00:00:18,140 PyCharm do when they have a suggestion about your code. So if we hover our mouse 4 00:00:18,140 --> 00:00:23,440 over that, you can see there it's saying simplified chained comparison. 5 00:00:23,440 --> 00:00:26,640 When dealing with numerical values in a condition, you can often replace 6 00:00:26,640 --> 00:00:31,699 and with a simpler comparison. So what I'm going to do is comment that line out and 7 00:00:31,699 --> 00:00:36,800 we're going to make this a bit simpler. So instead what we're going to type, 8 00:00:36,800 --> 00:00:46,780 is if 16 less that equal to age less than equal to 65 : 9 00:00:46,780 --> 00:00:51,940 So I think that's much easier to understand now because it's obvious that age is in the range 10 00:00:51,940 --> 00:00:57,460 of 16 to 65. The condition is the same as the previous one but it's phrased in a 11 00:00:57,469 --> 00:01:01,129 more understandable way. We should still test it, though, so I'm going to run the 12 00:01:01,129 --> 00:01:05,059 program and repeat the inputs that we've used previously. Alright, so when we ran it 13 00:01:05,059 --> 00:01:11,240 previously we tested a value between 16 and 65. I'll enter 34. That's working okay. 14 00:01:11,240 --> 00:01:15,770 We're getting the message printed out. So next if we run it again, we tested a value 15 00:01:15,770 --> 00:01:21,640 less than 16 and a value greater than 65. So I'm going to enter 12 for the first test 16 00:01:21,640 --> 00:01:26,000 and nothing's printed out, which is correct. Run it again. This time I'm going 17 00:01:26,000 --> 00:01:32,600 to enter 78. No output again, so that's correct, and the final two tests 18 00:01:32,600 --> 00:01:39,120 were to make sure the code works when we enter 16 and 65. So I'm going to do that, one at a time. 19 00:01:39,120 --> 00:01:46,100 16 works, 65, that also works. So alright, that's working fine. 20 00:01:46,100 --> 00:01:50,500 We could also turn the condition around or use or instead. As I've said a few times, 21 00:01:50,500 --> 00:01:54,640 there's often several ways to get the same result when you're programming. But let's 22 00:01:54,650 --> 00:01:58,220 make a change to the program now so that it prints a message when the condition's 23 00:01:58,220 --> 00:02:04,549 false, in other words, if age is outside of the range 16 to 65. So I'm going to come up end up put 24 00:02:04,549 --> 00:02:11,440 an else in there, so else : and on the next line indented, print parentheses 25 00:02:11,440 --> 00:02:18,660 and in double quotes I'm going to type Enjoy your free time, like so. 26 00:02:20,120 --> 00:02:23,600 Let's also, on line 9, put a row of dashes so that we can tell which 27 00:02:23,600 --> 00:02:26,920 block of code has produced which bit of output. So I'm going to type print 28 00:02:26,920 --> 00:02:32,120 parentheses double quotes and put a dash in the double quotes, and outside of the 29 00:02:32,120 --> 00:02:40,360 double quotes * 80. Let's have a go at doing this now, using or instead of and. 30 00:02:40,360 --> 00:02:48,920 So staying on line 11 I'm going to type if age less than 16 or age 31 00:02:48,920 --> 00:03:01,100 greater than 65 : Then we're going to type print Enjoy your free time, else 32 00:03:01,100 --> 00:03:08,820 print, on the next line, parentheses and double quotes, Have a good day at work. 33 00:03:08,820 --> 00:03:13,060 So now if age is less than 16, we're printing the message, Enjoy your free time. 34 00:03:13,060 --> 00:03:18,340 The code will do the same thing if the other part of the condition is true, if age is greater than 65. 35 00:03:18,340 --> 00:03:22,460 Now we're using or on line 11, which means we'll get that message if 36 00:03:22,460 --> 00:03:27,760 either of those conditions is true, as opposed to and, where they both needed to be true. 37 00:03:27,760 --> 00:03:32,300 If neither of them is true, we'll get the message in the else block. 38 00:03:32,300 --> 00:03:40,880 So let's run the program. I'm going to enter 16, and you can see we have a good day at work printed twice. 39 00:03:40,880 --> 00:03:44,060 Both bits of code are doing the same thing. If you recall, when 40 00:03:44,060 --> 00:03:48,660 we used and, and that's the code on line 4, both the conditions had to be true. 41 00:03:48,660 --> 00:03:53,630 With or, as you can see on line 11, Enjoy your free time will be printed if either 42 00:03:53,630 --> 00:03:58,180 condition is true. Generally, one way or the other will be more natural in some 43 00:03:58,190 --> 00:04:02,840 situations and which to use will depend on the context. There is one important 44 00:04:02,840 --> 00:04:07,240 difference, though, that's useful to be aware of. 45 00:04:07,240 --> 00:04:11,600 When comparing conditions using and, Python will stop checking as soon as it 46 00:04:11,600 --> 00:04:16,339 finds a condition that is False. When comparing conditions using or, it'll stop 47 00:04:16,339 --> 00:04:22,540 as soon as it finds one that's True. So looking at line 11, if age is less than 16, 48 00:04:22,540 --> 00:04:26,840 then Python doesn't have to check to see if it's also greater than 65. 49 00:04:26,840 --> 00:04:30,300 This can be very important and we'll be coming back to that later. 50 00:04:30,300 --> 00:04:34,980 For now, it's just something to be aware of. Right, so I'm going to stop the video here and in the next one, 51 00:04:34,980 --> 00:04:40,600 we're going to take a look at boolean values. See you in the next video.