WEBVTT 0 00:00.090 --> 00:01.080 In the last lesson, 1 00:01.170 --> 00:05.010 we looked at how to provide default values for optional arguments. 2 00:05.340 --> 00:08.100 In this lesson, we'll discuss how to create functions 3 00:08.190 --> 00:10.290 that can take any number of arguments. 4 00:10.800 --> 00:13.680 Let's say that we had a function called add, 5 00:13.980 --> 00:18.660 which adds n1 and n2 and it just returns the sum of those numbers. 6 00:19.020 --> 00:23.850 That's very well and good, but what if I wanted to add more than two numbers? 7 00:23.940 --> 00:28.080 Well, I would have to add n1, n2, n3, n4, 8 00:28.320 --> 00:31.020 but then I would have to add four numbers every single time. 9 00:31.500 --> 00:36.500 So what if I wanted to make this function more flexible and to allow any number 10 00:37.080 --> 00:40.740 of arguments to be used as the input? Well, 11 00:40.830 --> 00:45.750 what I can do is to simply change the code to use this asterix 12 00:45.900 --> 00:48.060 and then the name of my parameter. 13 00:48.810 --> 00:52.110 That name args is by convention 14 00:52.140 --> 00:57.120 what most Python developers will use. And it simply stands for arguments. 15 00:57.420 --> 01:00.120 But you don't have to stick with that naming if you don't want to. 16 01:01.230 --> 01:05.430 But what you do need is that asterix. That's the really important part. 17 01:05.910 --> 01:10.910 What that tells Python is this function add can accept any number of arguments. 18 01:13.110 --> 01:15.210 And once inside the function, 19 01:15.240 --> 01:17.850 you can actually loop through all of the arguments 20 01:18.090 --> 01:22.770 which is going to be in the form of a tuple and you can do whatever it is you 21 01:22.770 --> 01:24.690 want with each of those arguments. 22 01:25.140 --> 01:29.520 Instead of now passing in only two arguments because that was fixed 23 01:29.520 --> 01:34.200 when we created the function, we can now pass in any number of values 24 01:34.290 --> 01:36.660 like four values or seven values, 25 01:36.960 --> 01:41.640 and we can do whatever it is we want with them. Let's try this code out. 26 01:41.670 --> 01:44.940 I'm going to delete the code related to Python turtle, 27 01:45.300 --> 01:49.980 and I'm going to create a new file called playground.py. 28 01:50.640 --> 01:54.720 And we're going to use this playground.py to test out what we've just learned. 29 01:55.560 --> 01:59.820 I want you to have a think about what you just saw in the slides and see if you 30 01:59.820 --> 02:04.820 can create a function called add where you can pass in as many numbers as you 31 02:05.610 --> 02:06.420 want 32 02:06.420 --> 02:11.420 and it will always add together all of the numbers that are being passed into 33 02:12.060 --> 02:16.080 the function as the input, and then return the total 34 02:16.080 --> 02:19.470 sum. Pause the video and see if you can give that a go. 35 02:21.210 --> 02:21.600 All right. 36 02:21.600 --> 02:26.600 So what we want to do is to be able to call this method add, for example 37 02:26.790 --> 02:30.270 down here and pass in any number of values, right? 38 02:30.300 --> 02:32.550 Let's just go with three to begin with. 39 02:33.090 --> 02:38.090 And then we want to receive all of those values inside this function and then 40 02:38.400 --> 02:42.300 add them all together. So we're going to use that asterix trick. 41 02:42.450 --> 02:47.130 So one * and then we can give a name to the arguments that we receive, 42 02:47.490 --> 02:49.860 which normally is just called args. 43 02:51.450 --> 02:53.280 Now that we've got these args, 44 02:53.490 --> 02:58.490 if I actually go ahead and print it out and we go to run and then run and change 45 03:01.750 --> 03:06.640 this to our playground, you can see it's basically just printing out a tuple. 46 03:07.090 --> 03:11.410 And that tuple represents all the inputs that were passed in when this function 47 03:11.410 --> 03:13.900 was called. And in fact, 48 03:13.900 --> 03:18.840 if I do a time check on this args, you can see it 49 03:18.840 --> 03:21.850 is indeed a tuple. Now, 50 03:21.850 --> 03:26.140 once we've got hold of this args tuple, we can actually loop through it. 51 03:26.320 --> 03:30.610 So we can say for n in args, for 52 03:30.640 --> 03:35.260 each of the numbers in that tuple, let's go ahead and print each of them. 53 03:36.280 --> 03:39.940 You can see it's now separated them all out; three, five, and six. 54 03:40.270 --> 03:42.910 So that makes it easy enough for us to create the sum. 55 03:43.240 --> 03:45.700 So let's create a sum which is equal to zero. 56 03:46.060 --> 03:48.550 And then instead of printing out each of the n, 57 03:48.580 --> 03:53.560 we can just add the n to sum, and finally outside the loop 58 03:53.590 --> 03:55.600 we'll return our sum. 59 03:56.350 --> 04:00.880 So now when we print this final results by calling add three, five, 60 04:00.880 --> 04:04.750 six, you can see it's now added three, five, and six, 61 04:05.020 --> 04:09.220 and we can call this method in different ways. We can add more values to it, 62 04:09.460 --> 04:13.630 two and one, and you can see it's now equal to 17. 63 04:13.990 --> 04:18.990 And you can basically keep going because it can take any number of values. 64 04:19.780 --> 04:23.710 This is all done by this asterix keyword. 65 04:24.280 --> 04:29.280 And it basically packs all of these numbers that you've put in as the input into 66 04:30.070 --> 04:33.790 a tuple called whatever it is you want it to be called. 67 04:34.120 --> 04:37.660 So you can call it numbers if you want, or you can stick to the default, 68 04:37.690 --> 04:42.400 which is just args. And then once we've got that args inside the function, 69 04:42.430 --> 04:47.080 we loop through it and we can do whatever we want to each of the values. Now, 70 04:47.110 --> 04:48.640 in addition to looping through it, 71 04:48.670 --> 04:53.200 you can also access them by index because it's a tuple after all. 72 04:53.200 --> 04:57.250 So we can say args at position zero like this. 73 04:57.280 --> 04:58.780 And if I print that out, 74 04:59.260 --> 05:03.550 you'll see that the value is three because the first one is three. 75 05:04.390 --> 05:08.260 So that's why these unlimited arguments using this * 76 05:08.290 --> 05:12.340 args is also known as unlimited positional arguments, 77 05:12.610 --> 05:17.320 because the position of your arguments which you pass into the function 78 05:17.350 --> 05:22.350 matters' a huge deal because if I fetched the one at position one, 79 05:22.630 --> 05:25.030 it will no longer be three, and it'll now be five. 80 05:26.140 --> 05:31.140 So this is a way for us to be able to define a function and specify a unlimited 81 05:34.300 --> 05:38.980 or unspecified number of inputs. In other words, 82 05:39.070 --> 05:43.690 the number of arguments for the function can vary because the asterix operator 83 05:43.930 --> 05:47.860 collects all of the arguments into a tuple. However, 84 05:47.890 --> 05:52.720 what if we wanted to refer to our arguments by name rather than by position? 85 05:53.230 --> 05:56.140 Well, that is exactly what we'll talk about in the next lesson. 86 05:56.460 --> 05:57.010 So I'll see you there.