Let's cover a function that accepts multiple arguments, or parameters, or inputs. Those are interchangeable terms. In case you missed it, here are the previous parts of the series: Python for Beginners, Part 1: How to Download and Install Python Python for Beginners, Part 2: Hello World Exercise Python for Beginners, Part 3: The Turtle Module Python for Beginners, Part 4: Interactive Shell vs. Script Python for Beginners, Part 5: Variables Python for Beginners, Part 6: Strings Python for Beginners, Part 7: Fun Fun Functions Transcript 0:00 So, in the last video, we left off 0:02 at talking about how to make a function. 0:05 So, we wrapped up our square in a function, 0:09 and that way we were really easily able to use the square, 0:12 and this way we can use the square 0:14 as many times as we want and it's very easy. 0:18 So, let's do something cool. 0:21 I said let's talk about the idea of arguments 0:25 or parameters of a function. 0:27 What we want to be able to do is, let's say that, 0:30 instead of 100, what if we wanted to move 0:32 a different length every single time. 0:35 So, let's say we don't wanna be boring 0:38 and just move, I dunno, 100 steps. 0:42 So let's take a look at it, looks like we don't wanna move, 0:45 oh, I didn't call it anywhere. 0:47 Let's call it again, and I'm gonna remove this line here. 0:51 Okay, let's run it. 0:56 Okay, and let's say we don't wanna be boring 0:57 and make a really small square like this. 0:59 Let's say we wanna maybe go 200 steps, okay? 1:03 So, let's try it; let's go 200, 200, 200, and 200, 1:12 and let's take a look at what that looks like. 1:17 Nice, the square looks better. 1:20 Let's try to tweak it a little bit and let's make it, 1:22 I dunno, 240, 240, 240, 240. 1:34 Hmm, let's see; that looks pretty cool. 1:36 But what if I wanted a turtle to go 1:38 all the way to that edge perfectly, 1:41 and then go down, and then go to the left, 1:43 and then come back up. 1:45 Okay, let's try something; let's try 280, 280, 280, 280, 1:54 and hopefully ... oh, it's still not hitting the exact. 2:00 Maybe let's try 290 or something. 2:03 So, I hope that you're seeing that we have to change 2:05 these values here a lot, right? 2:09 We have to change it every single time. 2:12 And we have to change all four of them, 2:13 in all of those locations, which is kind of annoying. 2:17 So, how can we make it so we don't have to constantly 2:20 change all those values again and again? 2:25 It's kind of really frustrating. 2:27 We want to make it so we can just change it one time 2:30 and it changes it everywhere. 2:33 So, let's say, I dunno, let's call it n. 2:39 Let's make it a variable that's the same everywhere. 2:42 So let's just call it n, and I'm gonna make 2:45 a variable here, and I'm gonna call it n, 2:48 and I'm gonna say go 250, okay? 2:51 So, now, everywhere n is, we have 250, okay? 2:56 So let's try to run this bad boy now. 3:01 Okay, cool, 250. 3:03 Let's make that really small; let's say 50. 3:08 Okay, that was really small. 3:10 That's pretty cool, we were able to use that 3:13 and that made our life really easy. 3:16 But, a lot of the times, we don't wanna change 3:19 the function itself, like, the definition of the function. 3:22 Here, its job is to make a square, 3:25 and that's all it should need to know how to do. 3:28 And we wanna be able to give it something, 3:31 based on which it changes the length of it, right? 3:37 So, like, how far it goes or how big the square is. 3:42 Maybe you can think of it like, 3:46 in English, if you have a definition of a word 3:49 that you look up, once you learn that word, you can use it 3:53 in whatever way you want; it really depends on the context. 3:57 For example, if you wanna say, "Wow, man. You really 4:00 killed it," you're basically saying "You did 4:03 a really good job and you did amazing." 4:05 Or, if you said, "Aww, man. You just really killed that 4:08 thing for me, you know, you really killed it for me. 4:11 I don't even find it fun anymore." 4:13 Now you're using it and the context is basically 4:17 that somebody really made something less enjoy able 4:20 for you or discouraged you in some way. 4:23 So, the word kill, in this case, right, it has 4:27 a completely different meaning, but, based on the context, 4:30 we change it, right? 4:32 Depending on what context we give it, 4:34 we change the word kill. 4:36 But we shouldn't actually go and change the definition 4:38 of the word kill every time we want to use it 4:40 in a different context, okay? 4:42 So, what I'm trying to say here, is that, 4:44 instead of changing the function itself, 4:47 let's do something really cool, let's give it context. 4:51 I'm gonna say a square takes in some input n. 4:55 So, whatever n I give it, it just puts that in here. 4:59 And, instead of calling it n, let's make it more fun 5:02 and call it length. 5:04 So, everywhere I see n, I'm just 5:06 going to replace it with length. 5:09 So, now the cool thing that's gonna happen is, 5:11 if I give it the length of five, everywhere it sees length 5:14 it just replaces it with five. 5:17 If I give it the length of, let's say, I dunno, 200, 5:21 it'll go everywhere and replace everything with 200, okay? 5:25 That way we'll get a longer square. 5:28 So, let's try it. 5:30 If I run this right now, I'm gonna get an error, 5:32 and let's see why. 5:36 Okay, I got an error, and the error says, "TypeError, 5:40 the function square," that's what the parentheses 5:43 afterwards it means, "is missing one required 5:47 positional argument: length." 5:51 We're supposed to give it something, we're supposed 5:54 to give it context, right? 5:56 Like, the word kill, we gave it context 5:59 and it changes the whole meaning of the thing. 6:02 So, here, in square, we're going to give it 6:03 the length, so let's say for length we say 100. 6:07 Okay, now let's see what happens. 6:09 Let's run it, and we get a square 6:12 that it goes 100 in each direction, right? 6:15 So what just happened? 6:17 We passed in the 100 here, which really 6:20 passed in the 100 here, and since there's 100 here, 6:24 it became 100 everywhere else, and, 6:27 so, we got a square that was a size 100. 6:31 And we can effectively do the same thing. 6:33 If I give it a 300, that's probably 6:35 not even gonna fit on the screen. 6:39 Oh, it pretty much does. 6:42 It makes a bigger square, right? 6:45 So, now, the only place I have to change it is really here. 6:49 This thing's job is to, now, just make a square. 6:52 That's all it does. 6:54 And, here, we can tell it how big that square should be. 7:00 So, let's say that we say, "Make a square of 300," 7:05 and then "Make a square that's, I dunno, 150," 7:09 and then "Make a square that's 100." 7:13 Let's see what that does; let's see what that looks like. 7:18 Okay, that's 300, that's the 150 and that's the 50. 7:24 Whoa, that was cool, right? 7:27 That kind of ... it seemed like it was about 7:30 to make some kind of design right there. 7:33 Okay, so, hopefully you guys have a little bit more 7:37 of an understanding of how arguments work. 7:40 Just to take it maybe one step further, 7:43 think what if instead of these 90 degrees, 7:45 you wanted to be able to change the degrees. 7:48 Maybe we can go on here and say angle 7:54 and replace everywhere we see 90 with angle. 8:00 And, so now, we have to give our function not one, 8:04 but two arguments, okay? 8:08 So, let's say 300 and 90; so the 300 will replace 8:12 the length part, so everywhere there is length 8:15 it'll replace that with 300, and the 90 will replace 8:20 angle, so everywhere it says angle, 8:23 it'll replace that with 90. 8:24 How cool is that? 8:26 So, let's run this bad boy 8:29 and check out what it looks like. 8:31 We've seen this square before multiple times, 300. 8:34 But now, let's add a twist. 8:36 Let's make this 45 degrees, let's see what happens. 8:42 Oh, oh, I don't even know what it did. 8:46 Let's reduce the length so we can at least 8:48 see what it does, right? 8:51 Let's run it; whoa, that's kind of cool. 8:55 It didn't make a square, it did something weird with it. 9:00 Okay, so, I'm foreshadowing multiple arguments, 9:03 and in the next video we'll take more about it. 9:06 All right, guys, I'll see you there.

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