1 00:00:04,540 --> 00:00:08,710 In this video, we'll look at three operators that apply to strings. In fact, 2 00:00:08,710 --> 00:00:10,309 they apply to any sequence type. 3 00:02:13,700 --> 00:02:16,030 Alright, so back to the code. I'm going to create a new Python 4 00:02:16,030 --> 00:02:19,720 file called sequence operators. 5 00:02:28,980 --> 00:02:31,720 So we've already seen the plus operator used for 6 00:02:31,720 --> 00:02:35,800 strings to concatenate them. So let's just type in a few strings, so I'm gonna start 7 00:02:35,800 --> 00:02:42,489 with typing string1 equals "he's ", with a single quote there, but the 8 00:02:42,489 --> 00:02:47,890 string in double quotes, string2 equals "probably ", in double quotes, with a space 9 00:02:47,890 --> 00:02:54,730 after the y, string3 equals "pining ", with a space at the end of the letter g, 10 00:02:54,730 --> 00:03:03,790 string4 is equal to "for the " space, and double quote there, and then string5 equals double 11 00:03:03,790 --> 00:03:13,150 quotes "fjords", and then I'm going to print on line 7, string1 + string 2 + string3, 12 00:03:13,150 --> 00:03:23,180 whoops I put a space there, string3 + string4 + string5. 13 00:03:23,180 --> 00:03:28,720 But the plus isn't necessary when concatenating string literals, though, in Python, 14 00:03:28,720 --> 00:03:39,040 so we could also do print, so on line 9, double quotes he's space, then another space outside the 15 00:03:39,040 --> 00:03:44,280 double quotes, probably, space there, another closing off double quote, 16 00:03:44,280 --> 00:03:49,240 another set of double quotes but after a space there to separate it, pining space, 17 00:03:49,240 --> 00:03:53,770 whoops, space outside of the double quote 18 00:03:53,770 --> 00:03:59,950 for the and space space and Fjord's, not sure if I pronounced that correctly. 19 00:03:59,950 --> 00:04:03,040 Alright, 20 00:04:03,040 --> 00:04:05,920 so that'll print the same thing and if we run this, we should see both 21 00:04:05,920 --> 00:04:13,720 outputting the identical output, and obviously I made a typo. 22 00:04:13,720 --> 00:04:15,860 Run it again 23 00:04:15,860 --> 00:04:20,260 and we've got the identical output in both cases. So I mentioned this second way, 24 00:04:20,260 --> 00:04:23,800 because it's how Python works, not because we think you'd ever want to do 25 00:04:23,800 --> 00:04:26,290 something like that. I'm sure you'd agree that the first 26 00:04:26,290 --> 00:04:30,280 example on line 7 is a bit easier to read. Now with that said, strings can also 27 00:04:30,280 --> 00:04:35,920 be multiplied, which is a bit weird if you're coming from another programming language. 28 00:04:35,920 --> 00:04:41,110 I can come down on line 11, I can type print parentheses Hello in double 29 00:04:41,110 --> 00:04:47,840 quotes with a space before the closing double quote.Then I'm going to put * 5. 30 00:04:47,840 --> 00:04:51,940 Now you can't actually perform arithmetic multiplication on strings, of course. 31 00:04:51,940 --> 00:04:56,050 Instead what happens is, the star or multiplication operator repeats the 32 00:04:56,050 --> 00:04:59,700 sequence a certain number of times; 5 in this case. 33 00:04:59,700 --> 00:05:03,800 So if we run the code 34 00:05:03,800 --> 00:05:08,200 you can see we've got the word Hello printed, or outputted, five times. 35 00:05:08,200 --> 00:05:11,980 Now lists and tuples can also be multiplied, as we'll see when we look 36 00:05:11,980 --> 00:05:14,540 at those sequence types later in the course. 37 00:05:14,540 --> 00:05:18,520 You can't concatenate or multiply a range though, and that's not a problem 38 00:05:18,520 --> 00:05:22,390 because you probably wouldn't want to do that anyway. Now once again, operator 39 00:05:22,390 --> 00:05:28,800 precedence applies, so if I type some other code here, 40 00:05:28,800 --> 00:05:34,980 if I type print parentheses double quotes Hello, space before the closing double quote, 41 00:05:34,980 --> 00:05:43,140 multiplied by 5 plus 4. So this example wouldn't print Hello nine times, and again, we're 42 00:05:43,150 --> 00:05:46,330 talking about operator precedence there. So if we run this program, we'll see that 43 00:05:46,330 --> 00:05:50,520 we'll get an error, and the reason we're getting an error is because Hello, in 44 00:05:50,520 --> 00:05:55,390 double quotes, x 5 evaluates to a string, and then there's an attempt to then add 45 00:05:55,390 --> 00:06:00,789 the numeric number 4 to it and it fails for that reason. So what we can do is, I'm 46 00:06:00,789 --> 00:06:03,250 going to show you two things here, and they actually do different things. 47 00:06:03,250 --> 00:06:06,550 So firstly, I'm going to change line 13 to put five + four in 48 00:06:06,550 --> 00:06:12,130 parentheses, but then also I can type on line 14, print parentheses double quotes 49 00:06:12,130 --> 00:06:20,620 Hello space again and multiplied by 5, plus and 4 in double quotes. 50 00:06:20,620 --> 00:06:26,040 Now because of the parentheses, line 13 evaluates 5 + 4 to get 9, so it should 51 00:06:26,050 --> 00:06:31,300 then repeat the string 9 times. Line 14 should repeat the string 5 times 52 00:06:31,300 --> 00:06:34,750 and then append the string 4 to it, so let's just run that and confirm that's how it 53 00:06:34,750 --> 00:06:40,240 works, and can see that works, as I mentioned. Alright, so there's also an 54 00:06:40,240 --> 00:06:44,950 operator to check if one string is a sub-string of another. To do that, 55 00:06:44,950 --> 00:06:52,000 we actually check if one thing is in another. So let's start by typing some code. 56 00:06:52,000 --> 00:06:56,940 On line 16 I'm going to type, today equals Friday, and that's in double quotes 57 00:06:56,940 --> 00:07:01,840 because it's a string. 58 00:07:01,840 --> 00:07:05,720 Okay, next I'm going to type print parentheses double quotes, 59 00:07:05,720 --> 00:07:11,860 day in today, and put a comment here for each, which 60 00:07:11,860 --> 00:07:19,570 should be True, print fri in today, and obviously the first part's in double 61 00:07:19,570 --> 00:07:24,270 quotes, as you can see there. That should also be True; third example, print 62 00:07:24,270 --> 00:07:32,180 parentheses and we'll put t h u r in today, which should obviously be False, 63 00:07:32,180 --> 00:07:40,220 and lastly we do a print parentheses parrot in double quotes in double quotes fjord. 64 00:07:40,220 --> 00:07:43,860 That should also be False, 65 00:07:43,860 --> 00:07:50,060 and I'll just clean up these a little bit. 66 00:07:50,060 --> 00:07:54,780 So here, the in operator evaluates to True if the first thing exists in the second, 67 00:07:54,780 --> 00:07:59,520 and false otherwise. We'll be using that a lot when we look at conditions and for loops, 68 00:07:59,520 --> 00:08:03,300 and you'll get plenty of practice using it and see loads of real examples. 69 00:08:03,300 --> 00:08:06,220 So I'm not going to discuss it any further now, but we'll just run that to confirm we're 70 00:08:06,220 --> 00:08:10,510 getting the results that we think we should. You can see we get True, True, 71 00:08:10,510 --> 00:08:16,780 False, False, which goes in line with the code from 17 to 20, and getting the expected values. 72 00:08:16,780 --> 00:08:17,919 Alright so let's end the video here 73 00:08:17,919 --> 00:08:21,280 and in the next one, we're going to look at the various ways we can format 74 00:08:21,280 --> 00:08:25,740 strings, and some of the string methods that allow us to manipulate them. 75 00:08:25,740 --> 00:08:28,640 See you in the next video.