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These are the user uploaded subtitles that are being translated: 1 1 00:00:00,180 --> 00:00:01,770 Hi and welcome back. 2 2 00:00:01,770 --> 00:00:02,650 In this video, we're looking 3 3 00:00:02,650 --> 00:00:06,060 at default values for parameters. 4 4 00:00:06,060 --> 00:00:07,280 If you already know a bit of Python, 5 5 00:00:07,280 --> 00:00:10,506 you may wonder why we didn't cover this earlier. 6 6 00:00:10,506 --> 00:00:13,480 And quite simply the reason is that we didn't need it. 7 7 00:00:14,850 --> 00:00:16,570 Now we do and we're gonna start looking 8 8 00:00:16,570 --> 00:00:19,210 at a couple of instances where having default values 9 9 00:00:19,210 --> 00:00:21,010 with parameters is gonna be useful. 10 10 00:00:21,010 --> 00:00:22,890 So let's get right on it. 11 11 00:00:22,890 --> 00:00:25,180 Whenever we call a function that has parameters, 12 12 00:00:25,180 --> 00:00:29,180 we are expected to give it an equal number of parameters. 13 13 00:00:29,180 --> 00:00:33,080 We already know this, so I'll show you some example code. 14 14 00:00:33,080 --> 00:00:36,340 Here's some accounts, like a checking account. 15 15 00:00:36,340 --> 00:00:39,570 Let's see, that has $1,958 in it 16 16 00:00:39,570 --> 00:00:42,940 or pounds if you're in the UK. 17 17 00:00:42,940 --> 00:00:46,490 3695.50 in your savings. 18 18 00:00:46,490 --> 00:00:49,330 That's a pretty respectable amount of money. 19 19 00:00:49,330 --> 00:00:52,160 Then we're gonna have a function add_balance, 20 20 00:00:52,160 --> 00:00:53,360 which is going to take an amount, 21 21 00:00:53,360 --> 00:00:55,090 which is going to be a float and a name, 22 22 00:00:55,090 --> 00:00:56,090 which is going to be a string. 23 23 00:00:56,090 --> 00:00:57,740 And it's going to return a float. 24 24 00:00:58,850 --> 00:01:01,330 The reason I'm including it here, 25 25 00:01:01,330 --> 00:01:03,830 the type hinting that we've looked at in the past. 26 26 00:01:05,190 --> 00:01:08,050 Also, just for completeness, I am going to say function 27 27 00:01:08,050 --> 00:01:10,810 to update the balance of an account 28 28 00:01:10,810 --> 00:01:12,830 and return the new balance. 29 29 00:01:14,060 --> 00:01:15,660 Include that log string in there 30 30 00:01:15,660 --> 00:01:18,780 just so you know what this function's all about. 31 31 00:01:18,780 --> 00:01:21,300 As you can see, this function, add_balance, 32 32 00:01:21,300 --> 00:01:23,710 is going to update the balance of an account 33 33 00:01:23,710 --> 00:01:25,850 and return the new balance. 34 34 00:01:25,850 --> 00:01:29,050 The two arguments it takes are the amount 35 35 00:01:29,050 --> 00:01:31,220 to increase the balance by 36 36 00:01:31,220 --> 00:01:33,660 and the name of the account that we're gonna change. 37 37 00:01:33,660 --> 00:01:37,250 Then it's gonna go over to your accounts global dictionary 38 38 00:01:37,250 --> 00:01:39,200 and it's going to change it. 39 39 00:01:39,200 --> 00:01:43,240 So, accounts name 40 40 00:01:43,240 --> 00:01:45,390 plus equal amount 41 41 00:01:45,390 --> 00:01:47,000 and then it's going to return accounts name. 42 42 00:01:47,000 --> 00:01:49,660 It's going to return the new balance of the account. 43 43 00:01:51,210 --> 00:01:52,930 Accounts name, for example, for checking 44 44 00:01:52,930 --> 00:01:54,860 is going to be 1958. 45 45 00:01:54,860 --> 00:01:57,510 Let's say we say 200 in here is gonna go, 46 46 00:01:57,510 --> 00:01:58,570 increase it by 200. 47 47 00:01:58,570 --> 00:02:00,910 I'm not even gonna try to do the math here. 48 48 00:02:00,910 --> 00:02:02,450 Then it's going to return the new amount 49 49 00:02:02,450 --> 00:02:04,690 of accounts name, so that should be a float. 50 50 00:02:06,600 --> 00:02:09,230 However, what we can do, of course, 51 51 00:02:09,230 --> 00:02:13,950 is add balance 500.00 to savings 52 52 00:02:13,950 --> 00:02:16,900 and then print account savings 53 53 00:02:16,900 --> 00:02:18,670 and it should tell us the new balance 54 54 00:02:18,670 --> 00:02:20,450 which should be in the four thousands. 55 55 00:02:21,320 --> 00:02:23,020 Oh, sorry, accounts savings. 56 56 00:02:25,145 --> 00:02:27,190 As you can see, 4,195.5. 57 57 00:02:28,500 --> 00:02:30,440 Notice how the zero at the end gets dropped, 58 58 00:02:30,440 --> 00:02:32,360 but in my code I like having two decimal places 59 59 00:02:32,360 --> 00:02:34,770 for currency just to keep things clearer. 60 60 00:02:36,270 --> 00:02:39,940 What you didn't know that you could do is you can say 61 61 00:02:39,940 --> 00:02:44,370 that by default, all new balances are going to go 62 62 00:02:44,370 --> 00:02:45,620 to your checking account. 63 63 00:02:47,100 --> 00:02:52,100 So the name here is going to be checking, by default. 64 64 00:02:53,540 --> 00:02:58,470 And the way we do that is we add equal checking. 65 65 00:03:00,250 --> 00:03:01,980 Okay, so the name is a string 66 66 00:03:01,980 --> 00:03:04,010 and its' default value is checking. 67 67 00:03:05,170 --> 00:03:07,960 That means that if we do not pass a string 68 68 00:03:07,960 --> 00:03:10,880 through this argument, which we can do now, 69 69 00:03:10,880 --> 00:03:12,650 we can not pass a string to it. 70 70 00:03:12,650 --> 00:03:14,150 We can not pass anything to it 71 71 00:03:15,040 --> 00:03:17,660 and we print out the checking at the end, 72 72 00:03:17,660 --> 00:03:21,700 we should see it has increased by $500, 73 73 00:03:21,700 --> 00:03:23,000 not 500 units. 74 74 00:03:24,270 --> 00:03:26,140 If you don't wanna use type hinting, 75 75 00:03:26,140 --> 00:03:27,960 then all you have to do is get rid of that. 76 76 00:03:27,960 --> 00:03:31,280 Okay and this stays the same, name equals checking. 77 77 00:03:31,280 --> 00:03:33,370 And that's that, okay. 78 78 00:03:35,090 --> 00:03:36,920 Frequently, actually, if you don't have type hinting, 79 79 00:03:36,920 --> 00:03:40,000 you'll see this written like so, without the spaces 80 80 00:03:40,000 --> 00:03:41,230 and when you do have type hinting, 81 81 00:03:41,230 --> 00:03:43,530 you'll see it written like so, all with spaces. 82 82 00:03:43,530 --> 00:03:45,850 It's up to you how many spaces you want 83 83 00:03:45,850 --> 00:03:47,150 to put in there, whether you wanna put spaces 84 84 00:03:47,150 --> 00:03:49,050 or not spaces, totally fine. 85 85 00:03:51,590 --> 00:03:53,190 Now, something important that you have to know 86 86 00:03:53,190 --> 00:03:55,930 about these names arguments, this is what they're called 87 87 00:03:55,930 --> 00:03:59,430 as soon as you have the default argument there, 88 88 00:03:59,430 --> 00:04:02,870 is that you cannot have this 89 89 00:04:04,390 --> 00:04:07,130 here, oops sorry, 90 90 00:04:07,130 --> 00:04:09,660 you cannot have this here. 91 91 00:04:12,050 --> 00:04:13,820 This will be illegal. 92 92 00:04:13,820 --> 00:04:16,200 When you run it, it'll tell you here. 93 93 00:04:16,200 --> 00:04:18,580 Syntax error, known default argument 94 94 00:04:18,580 --> 00:04:20,320 follows default argument. 95 95 00:04:20,320 --> 00:04:21,950 So you cannot do this. 96 96 00:04:21,950 --> 00:04:23,870 Any argument that has a default value 97 97 00:04:24,840 --> 00:04:27,740 has to follow arguments that do not 98 98 00:04:27,740 --> 00:04:28,573 have default values. 99 99 00:04:28,573 --> 00:04:29,480 So in this case, the amount 100 100 00:04:29,480 --> 00:04:31,240 does not have a default value. 101 101 00:04:31,240 --> 00:04:34,030 The name does, so the name has to go at the end. 102 102 00:04:34,030 --> 00:04:35,280 If you have many arguments, 103 103 00:04:35,280 --> 00:04:38,860 some of which have default values, 104 104 00:04:38,860 --> 00:04:40,260 they must all go at the end. 105 105 00:04:41,240 --> 00:04:42,073 Okay? 106 106 00:04:43,280 --> 00:04:44,113 That's it. 107 107 00:04:44,113 --> 00:04:46,350 This is default values for arguments. 108 108 00:04:46,350 --> 00:04:48,620 You can have many arguments, many default values. 109 109 00:04:48,620 --> 00:04:50,130 One default value per argument, 110 110 00:04:50,130 --> 00:04:52,460 of course and we're gonna learn more 111 111 00:04:52,460 --> 00:04:53,530 about these default values 112 112 00:04:53,530 --> 00:04:56,340 and how to use them in subsequent videos, 113 113 00:04:56,340 --> 00:04:57,490 in just a couple of videos. 114 114 00:04:57,490 --> 00:04:58,510 In fact, in the next video, 115 115 00:04:58,510 --> 00:05:00,210 and in coming videos too. 116 116 00:05:00,210 --> 00:05:01,290 So, that's it for this one. 117 117 00:05:01,290 --> 00:05:02,670 I'll see you on the next one. 9746