1 00:00:00,660 --> 00:00:08,760 When you go to order a coffee to the barista, do you say I want a coffee or do you say I want a coffee 2 00:00:08,760 --> 00:00:09,600 in a cup? 3 00:00:11,150 --> 00:00:16,280 Whatever you would say in both cases, you would always get a coffee in a cup. 4 00:00:17,620 --> 00:00:25,420 So people don't say, I want the coffee in a cup, because that is the default argument. 5 00:00:25,420 --> 00:00:27,640 So it is a default input. 6 00:00:28,870 --> 00:00:33,550 The barista always knows that the coffee should be served in a cup. 7 00:00:33,850 --> 00:00:35,890 The same goes in here. 8 00:00:36,520 --> 00:00:40,660 We always use this to do that text file. 9 00:00:40,660 --> 00:00:48,820 So why should we mention it always when when we order the function, When we call the function, when 10 00:00:48,820 --> 00:00:50,020 we order the coffee. 11 00:00:51,280 --> 00:00:55,120 So we do that here and there and there multiple times. 12 00:00:56,780 --> 00:01:03,740 Well, there is a solution for that, and the solution is default arguments or default parameters, 13 00:01:03,740 --> 00:01:05,930 whatever terminology you use. 14 00:01:06,200 --> 00:01:08,510 I'll explain the terminology as well. 15 00:01:09,590 --> 00:01:12,680 So to make this a default parameter. 16 00:01:14,870 --> 00:01:18,640 All you have to do and let's start with get to this function. 17 00:01:18,650 --> 00:01:24,110 All you have to do is assign the value to dos the text to the parameter. 18 00:01:24,770 --> 00:01:33,350 So now this is a default parameter, and therefore we say that this call has a default argument. 19 00:01:33,350 --> 00:01:38,570 So we don't have to provide the actual value of the argument. 20 00:01:38,990 --> 00:01:43,460 So in this case, both terminologies are used interchangeably. 21 00:01:44,120 --> 00:01:46,340 Default argument, default parameter. 22 00:01:47,420 --> 00:01:56,240 So therefore we can remove all these argument values from all the get to this function, which is four 23 00:01:56,240 --> 00:01:58,730 of them like that. 24 00:02:00,190 --> 00:02:02,470 And here as well, the fourth one. 25 00:02:04,450 --> 00:02:10,030 So if I run the code now and I try, for example, the show methods, things will work the same. 26 00:02:14,220 --> 00:02:24,210 The benefits here is that if you ever want to change the value of that parameter, you can simply specify 27 00:02:24,210 --> 00:02:24,930 the new value. 28 00:02:24,930 --> 00:02:29,580 For example, let's say to use one dot text. 29 00:02:30,300 --> 00:02:38,310 So I just changed the value in the get to this call in that condition. 30 00:02:38,310 --> 00:02:44,190 So let me try the code now, run mine and I'll try to add something so that this line is executed. 31 00:02:44,190 --> 00:02:50,550 So add my new to do press enter and we get an error this time. 32 00:02:50,550 --> 00:02:57,420 So it says that no such file or directory to this one dot text the error. 33 00:03:00,150 --> 00:03:02,190 Can be traced in here. 34 00:03:02,190 --> 00:03:05,580 So first it occurred in line. 35 00:03:06,430 --> 00:03:07,630 19. 36 00:03:09,610 --> 00:03:12,160 So errors can be read from top to bottom. 37 00:03:12,160 --> 00:03:13,840 So this is where the error started. 38 00:03:13,840 --> 00:03:15,850 Line 19 and here. 39 00:03:16,690 --> 00:03:23,230 So Python try to call this function and this function itself try to call something else which you see 40 00:03:23,230 --> 00:03:23,650 in here. 41 00:03:23,650 --> 00:03:25,030 So line two. 42 00:03:26,470 --> 00:03:28,570 Is the next one to be executed. 43 00:03:28,600 --> 00:03:29,800 So this one here. 44 00:03:30,810 --> 00:03:38,790 And that line tried to open the two does one the text file, which does not exist. 45 00:03:38,820 --> 00:03:42,720 That's why we get this error in line two. 46 00:03:44,690 --> 00:03:50,600 So what I'm trying to demonstrate here is that you can change default arguments. 47 00:03:50,600 --> 00:03:56,890 You can just give a value here, and that value will replace that value there. 48 00:03:58,310 --> 00:04:00,650 So that's the idea with two fold arguments. 49 00:04:02,470 --> 00:04:07,180 So let me go back here and remove that one and remove the value itself. 50 00:04:07,180 --> 00:04:08,200 We don't need it. 51 00:04:11,260 --> 00:04:17,209 And let's implement default parameters with the right to this function here as well. 52 00:04:17,230 --> 00:04:22,990 So file path would be to do the text. 53 00:04:25,580 --> 00:04:37,760 But to dos or is not a default parameter because we're always having a different list in each of these 54 00:04:37,760 --> 00:04:38,540 conditions. 55 00:04:38,540 --> 00:04:43,070 So in this add condition, the user adds a to do. 56 00:04:43,310 --> 00:04:51,020 They provide it in the command line and then we read the existing to dos using that get to this function 57 00:04:51,050 --> 00:04:55,760 up here and then we append the to do of the user to the list. 58 00:04:55,940 --> 00:05:00,620 So now we have a new list here and we want to provide that new list. 59 00:05:01,860 --> 00:05:03,870 To the right to this function. 60 00:05:03,870 --> 00:05:11,820 So there's no way for the right to do this function to have an assumption on what this value could be. 61 00:05:12,660 --> 00:05:15,660 So there is no assumption you want to keep. 62 00:05:16,540 --> 00:05:17,860 Parameters as. 63 00:05:18,920 --> 00:05:21,560 Non default parameters. 64 00:05:21,650 --> 00:05:23,690 So that is a default parameter. 65 00:05:23,690 --> 00:05:25,850 That is a known default parameter. 66 00:05:26,390 --> 00:05:32,120 Now we have this error here, so it says non default parameter follows default parameters. 67 00:05:32,120 --> 00:05:40,940 So this is a problem and it can be fixed by putting this non default parameter before the default parameters. 68 00:05:40,940 --> 00:05:44,480 So that is the correct syntax. 69 00:05:44,480 --> 00:05:46,970 Otherwise you will get an error. 70 00:05:51,720 --> 00:05:56,130 That also means that you should change the positions of these. 71 00:05:58,120 --> 00:06:06,280 Arguments when you call the function, because what's happening now is if I run the script, run main 72 00:06:06,550 --> 00:06:17,380 and I add my new to do so, we get an error and it started in line. 73 00:06:18,430 --> 00:06:19,570 23. 74 00:06:20,850 --> 00:06:21,510 And here. 75 00:06:21,510 --> 00:06:29,490 So this is the function code we just wrote, and then it traces back to line eight where the function 76 00:06:29,490 --> 00:06:30,780 definition is. 77 00:06:33,250 --> 00:06:39,700 And the error is that this function expected a string, right? 78 00:06:39,700 --> 00:06:42,610 Like to dos the text, for example. 79 00:06:42,640 --> 00:06:45,250 But in reality it got a list. 80 00:06:45,250 --> 00:06:50,410 And that is because the order of the arguments matter here. 81 00:06:50,590 --> 00:06:52,930 So if this is a first. 82 00:06:54,350 --> 00:06:55,490 Value you place. 83 00:06:55,520 --> 00:07:00,980 That value will go as the value of the first parameter. 84 00:07:00,980 --> 00:07:03,380 So to do arc is actually. 85 00:07:04,200 --> 00:07:08,250 The string while fall path is going to be the list. 86 00:07:09,430 --> 00:07:13,120 So basically what we did is we set five paths. 87 00:07:13,480 --> 00:07:19,690 Five path is equal to the list, which had like multiple to dos to do one and so on. 88 00:07:20,980 --> 00:07:21,780 That's what we did. 89 00:07:21,790 --> 00:07:30,220 So the open function is confused and it cannot open a file which has a path, a list, so it doesn't 90 00:07:30,220 --> 00:07:30,970 make sense. 91 00:07:31,420 --> 00:07:34,540 Therefore, you should respect the older now. 92 00:07:35,690 --> 00:07:37,640 To do should go first. 93 00:07:41,760 --> 00:07:50,580 And then to reduce the text or or if you don't like order, what you could do is you could. 94 00:07:52,400 --> 00:07:53,990 Let me undo this. 95 00:07:55,610 --> 00:08:03,350 So if you really want to have the order as you wish, then you could say fault path is equal to that 96 00:08:03,950 --> 00:08:04,730 and to do. 97 00:08:05,330 --> 00:08:07,430 Org is equal to that. 98 00:08:07,640 --> 00:08:12,740 So if you explicitly mention the argument names, then you don't have to respect the order. 99 00:08:12,770 --> 00:08:14,300 This will work now. 100 00:08:17,180 --> 00:08:20,300 So show and add new order. 101 00:08:21,710 --> 00:08:24,560 And new order is part of the two two items. 102 00:08:26,060 --> 00:08:31,310 However, I wouldn't recommend this method unless you have to. 103 00:08:34,390 --> 00:08:35,710 So just say. 104 00:08:39,100 --> 00:08:45,580 To do so first and then to dos the text. 105 00:08:49,540 --> 00:08:55,390 So to do that goes to to to talk to those that text goes to file path. 106 00:08:55,750 --> 00:09:03,160 Actually, since file path is default as is a default parameter, you don't even have to pass file path. 107 00:09:03,170 --> 00:09:05,350 So you just say to dos and that's it. 108 00:09:05,890 --> 00:09:09,220 So if I run the ad. 109 00:09:10,490 --> 00:09:14,140 We just made a default talk 110 00:09:16,490 --> 00:09:20,210 show and that's the new to do. 111 00:09:25,310 --> 00:09:31,760 So what we did is now we only mention that file path in there because it is not important. 112 00:09:31,760 --> 00:09:36,320 We don't have to pollute our code with unnecessary details all the time. 113 00:09:36,470 --> 00:09:39,260 Just like the cup, the coffee cup example. 114 00:09:39,260 --> 00:09:40,820 You don't have to say all the time. 115 00:09:40,820 --> 00:09:45,650 I want the coffee in a cup because that's the default behavior. 116 00:09:46,430 --> 00:09:51,000 So let's see, what else should we change here, right to do? 117 00:09:51,440 --> 00:09:59,090 Just remove to use the text and leave only that same here. 118 00:10:05,220 --> 00:10:06,240 And that's about it. 119 00:10:07,750 --> 00:10:15,610 Before I close the video, I want to also emphasize that I also built in functions can have default 120 00:10:15,610 --> 00:10:16,350 parameters. 121 00:10:16,360 --> 00:10:24,940 For example, if you say help input, you see the help string of the input function, you'll see that 122 00:10:24,940 --> 00:10:26,230 the prompt. 123 00:10:28,120 --> 00:10:32,560 Parameter is set by default to a non object. 124 00:10:34,270 --> 00:10:41,200 So that makes it possible for you to just say inputs without providing a string. 125 00:10:42,480 --> 00:10:49,080 So if you say like that, there will not be any string printed out here, no prompt. 126 00:10:49,080 --> 00:10:51,450 You just enter this as a user and so on. 127 00:10:51,570 --> 00:10:57,120 But if you provide that string, that string will be displayed in here. 128 00:11:01,010 --> 00:11:06,660 Some functions, though, such as Len. 129 00:11:06,860 --> 00:11:12,250 So this is a function that returns the length of a list or a string. 130 00:11:12,260 --> 00:11:13,340 So, for example. 131 00:11:13,400 --> 00:11:14,090 Hello? 132 00:11:14,120 --> 00:11:18,350 It tells you it has five items, so five characters. 133 00:11:18,350 --> 00:11:21,020 So if you do help. 134 00:11:23,330 --> 00:11:27,560 Len, you'll see that this doesn't have a default parameter. 135 00:11:28,610 --> 00:11:31,700 So the object is mandatory. 136 00:11:33,320 --> 00:11:37,970 That means if you do, Len, with votes and arguments, you're going to get an error. 137 00:11:38,780 --> 00:11:43,280 You see, Len takes exactly one argument, but you didn't give anything. 138 00:11:45,970 --> 00:11:55,990 We would get the same error if we change this, get to this function, to this. 139 00:11:56,410 --> 00:12:04,360 So if you just leave file path as a non default argument, then in get to dos, you don't mention the 140 00:12:04,360 --> 00:12:09,100 value of that file path and if you execute the code now. 141 00:12:11,110 --> 00:12:20,350 And you try to add a brand new to do you get an error in line 19 here. 142 00:12:20,860 --> 00:12:29,230 So the function called tried to execute the function definition, but it couldn't because the function 143 00:12:29,230 --> 00:12:33,460 calls should have gotten one argument file path. 144 00:12:36,280 --> 00:12:46,960 So I hope that makes sense that if you have a default value for the parameter, then you don't have 145 00:12:46,960 --> 00:12:50,050 to pass it here, otherwise you will get an error. 146 00:12:51,070 --> 00:12:52,660 So that's about this video. 147 00:12:52,780 --> 00:12:53,470 Thanks a lot. 148 00:12:53,500 --> 00:12:54,160 See you later.