1 00:00:04,700 --> 00:00:09,840 In the last video, I ended by talking about the term Augmented assignment 2 00:00:09,840 --> 00:00:14,660 IntelliJ and PyCharm highlight errors in our code. They also show warnings 3 00:00:14,660 --> 00:00:19,720 sometimes, to indicate possible problems with our code, even if it compiles 4 00:00:19,720 --> 00:00:24,240 successfully. The third thing it can flag up are suggestions. These are ways that 5 00:00:24,240 --> 00:00:28,440 we can improve our code, and you should generally pay attention to them. Now that 6 00:00:28,440 --> 00:00:31,920 doesn't mean you have to accept them - it's your code, after all - but most of the 7 00:00:31,920 --> 00:00:35,550 time, the suggestions will improve your code and are based on best programming 8 00:00:35,550 --> 00:00:41,250 practices. Now I can't show you this particular suggestion, but if you're on a Mac or 9 00:00:41,250 --> 00:00:45,510 Linux machine, most likely when you hover over line 27, it'll say assignment can 10 00:00:45,510 --> 00:00:50,399 be replaced with augmented assignment, and I touched on that phrase briefly in 11 00:00:50,399 --> 00:00:54,000 the previous section. I mentioned that I'd explain it more later so let's see 12 00:00:54,000 --> 00:00:58,289 what this is all about. Well augmented assignment sounds really 13 00:00:58,289 --> 00:01:03,020 fancy, but it's just a shorthand way of assigning values to a variable. 14 00:01:03,020 --> 00:01:08,040 The Python documentation describes augmented assignment as the combination, in a 15 00:01:08,040 --> 00:01:13,110 single statement, of a binary operation and an assignment statement, which is 16 00:01:13,110 --> 00:01:19,780 true but not terribly understandable. So looking at the code on line 27 there, 17 00:01:19,780 --> 00:01:24,390 guesses equals guesses plus 1, we're performing an addition. We take the value 18 00:01:24,390 --> 00:01:28,350 of guesses and add 1 to it. We then bind the variable guesses to the 19 00:01:28,350 --> 00:01:33,659 result. guesses becomes one greater than what it was. The addition is the binary 20 00:01:33,659 --> 00:01:38,009 operation, binary because it takes two operands to work on, and then there is an 21 00:01:38,009 --> 00:01:43,200 assignment. So going back to our code, to change this code on line 27 to an 22 00:01:43,200 --> 00:01:47,960 augmented assignment, we'll write it this way: so I want to comment that line out. 23 00:01:47,960 --> 00:01:57,020 On line 28 I'm gonna type guesses plus equals 1, and that's shorthand for what 24 00:01:57,030 --> 00:02:03,209 we had previously. If you were programming in Java or C++, IntelliJ 25 00:02:03,209 --> 00:02:07,349 wouldn't have suggested this change. That's because, in those languages, both 26 00:02:07,349 --> 00:02:11,940 statements are in fact identical. Their use is just a matter of preference or style. 27 00:02:11,940 --> 00:02:16,220 In Python, however, the augmented assignment form only evaluates the 28 00:02:16,220 --> 00:02:22,760 assignee, guesses in our example, once. In the other form, where guess has appeared twice, 29 00:02:22,760 --> 00:02:27,320 the variable is evaluated once each time it happens, and that's less 30 00:02:27,320 --> 00:02:33,060 efficient. Now I'll admit that the evaluation isn't very complicated here. 31 00:02:33,060 --> 00:02:36,690 After all, it's not like we're doing some complex calculation - you know, something like 32 00:02:36,690 --> 00:02:42,180 12 times 850 plus 13 million divided by 18 is obviously going to take 33 00:02:42,180 --> 00:02:47,940 a bit of time to work out. So evaluating a variable - what do I mean by that? Well 34 00:02:47,940 --> 00:02:52,319 evaluating a variable basically consists of looking up its value. That's pretty 35 00:02:52,319 --> 00:02:57,180 fast, and probably takes a small fraction of a millisecond. But doing it twice, when 36 00:02:57,180 --> 00:03:02,040 you could just do it once, is obviously less efficient. If you do that in a loop, 37 00:03:02,040 --> 00:03:07,950 going round, say, a million times, you could be wasting a second or more. Now in 38 00:03:07,950 --> 00:03:11,819 terms of efficiency, that might not sound bad, unless your code's trying to land an 39 00:03:11,819 --> 00:03:16,889 aeroplane. A jumbo jet can travel at over 600 miles per hour. At that speed, 40 00:03:16,889 --> 00:03:22,590 one second represents one sixth of a mile, or about 268 meters. Of course, if 41 00:03:22,590 --> 00:03:25,860 your code's trying to land an aeroplane without slowing it down first, then you've 42 00:03:25,860 --> 00:03:30,060 probably got more serious problems than missing an augmented assignment. 43 00:03:30,060 --> 00:03:34,950 But hopefully, you get the point here. There's also another reason why 44 00:03:34,950 --> 00:03:40,300 augmented assignment is more efficient in Python. With our first form on line 27 45 00:03:40,300 --> 00:03:45,020 Python creates a new variable. It binds that new variable to the result of 46 00:03:45,020 --> 00:03:50,400 performing the calculation, then destroys the original variable. 47 00:03:50,400 --> 00:03:54,459 Using an Augmented assignment, you can perform the operation in-place where 48 00:03:54,459 --> 00:03:59,560 possible, modifying the original variable instead of creating a new one. Now this 49 00:03:59,560 --> 00:04:03,880 isn't always possible, depending on the type of object, the variable, in question, 50 00:04:03,880 --> 00:04:07,500 but it will be done in place whenever possible. Alright, so let's switch back to 51 00:04:07,510 --> 00:04:11,349 the code. So Intellij suggests that you use 52 00:04:11,349 --> 00:04:15,609 augmented assignments in your Python code, rather than the longhand version 53 00:04:15,609 --> 00:04:20,040 that we used on line 27, because ultimately, they're more efficient. 54 00:04:20,040 --> 00:04:24,099 The term augmented assignment sounds far more complicated than it really is. 55 00:04:24,099 --> 00:04:27,310 The symbol for them is just the binary operator plus minus multiplication 56 00:04:27,310 --> 00:04:32,020 divide, followed by an equal sign. You can see the example there on line 28. 57 00:04:32,020 --> 00:04:42,220 Alright so let's create a new Python file. I'm gonna call it aa, and I'm gonna 58 00:04:42,220 --> 00:04:48,009 paste in some code, just to save a bit of time in the video. Okay, so there's the 59 00:04:48,009 --> 00:04:51,960 code there. Now what I've done is, I've added comments to the right of the code, 60 00:04:51,960 --> 00:04:57,190 to show the results we'll get from each augmented assignment. So it's easier to see 61 00:04:57,190 --> 00:05:01,720 that these augmented assignments relate directly to a normal assignment. 62 00:05:01,720 --> 00:05:05,400 They're easier to type, and as they're also more efficient, it makes sense really to 63 00:05:05,400 --> 00:05:12,180 use them. So let's run the program, just to confirm we get the expected values for x. 64 00:05:13,060 --> 00:05:16,800 You can see the values there. Scrolling down we've got 24, 20 for the 65 00:05:16,800 --> 00:05:28,840 various operations, 100, 25, 5, noting this one's now a float, 25.0, and the last value, 0.0. 66 00:05:29,400 --> 00:05:32,520 Alright, so we've seen two binary operations that can be performed 67 00:05:32,520 --> 00:05:37,540 on strings; concatenation and repetition. They can also be performed using 68 00:05:37,540 --> 00:05:41,560 augmented assignment. So let's actually type in some code here, and have a look 69 00:05:41,560 --> 00:05:49,080 at that. On line 24, I'm going to type greeting equals Good in double quotes. 70 00:05:49,080 --> 00:05:58,080 Line 26, greeting plus equals morning, and what I'm going to do there is, on line 24, 71 00:05:58,080 --> 00:06:02,360 put a space before the double quote. Moving on, I'm going to print greeting, 72 00:06:02,369 --> 00:06:08,649 print parentheses greeting, just scroll up a bit more, and on line 29 I'm gonna type 73 00:06:08,649 --> 00:06:21,129 greeting star equals 5, print greeting. Alright, so if we run the program again now, you can 74 00:06:21,129 --> 00:06:24,309 see the output down the bottom of the screen. Firstly, we get Good morning 75 00:06:24,309 --> 00:06:30,309 printed out - a combination of the word Good on line 24 and morning on line 26 using 76 00:06:30,309 --> 00:06:34,659 augmented assignment. But then also, on line 29, we've used augmented assignment 77 00:06:34,659 --> 00:06:38,289 and you can see we've now got five versions of Good morning showing on the 78 00:06:38,289 --> 00:06:42,610 second line, or the last line, of output before the program ended. And we saw that 79 00:06:42,610 --> 00:06:46,280 as well, in the last section and this is the augmented assignment way of 80 00:06:46,280 --> 00:06:50,520 performing both of these things - these two operations - concatenation and 81 00:06:50,520 --> 00:06:55,059 repetition with strings. Now there's five more binary operations that we haven't 82 00:06:55,060 --> 00:06:59,060 looked at, for manipulating individual bits as well as a matrix multiplication 83 00:06:59,060 --> 00:07:03,879 operator, but we'll leave them for a later video. So all the binary operators 84 00:07:03,879 --> 00:07:08,229 can be used in augmented assignment, and we can see the full list at the operator 85 00:07:08,229 --> 00:07:12,400 precedence table, which we looked at before. Let's just open that up again. 86 00:07:12,400 --> 00:07:17,379 Loading a browser I'll paste in the link, in the resources section as well, and 87 00:07:17,380 --> 00:07:23,740 it's in section 6.16 down the end of the page, so let's do a quick search for that. 88 00:07:23,740 --> 00:07:27,159 Okay, there's operator precedence again, towards the bottom. So you can check out 89 00:07:27,159 --> 00:07:31,809 the binary operators on this page. And again, all the binary operators can be 90 00:07:31,809 --> 00:07:36,610 used in augmented assignment. Alright, so moving on. In the next video, we'll take a 91 00:07:36,610 --> 00:07:40,100 break from coding and have a look at the style of the code that we write. 92 00:07:40,100 --> 00:07:43,020 See you in the next video.