In this one, we explore the concept of looping constructs, visually, in computer programming. 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 Python for Beginners, Part 8: Function Arguments Transcript 0:00 Okay, so now that we've talked a little bit 0:03 about functions with their arguments 0:05 and also a little bit about functions 0:07 with multiple arguments, this naturally leads us 0:11 to the next thing. What if I want to make that one square 0:16 but I want to make it multiple times? 0:19 Sure, I can copy it and paste this line 0:23 and paste it again, right, 0:26 and then paste it again, 0:28 so and and so forth. So, for example, 0:30 let's try having it pasted twice. 0:33 I'm gonna remove these comments here, 0:36 and just so you remember, this 50 goes in for the length, 0:40 it replaces every part of the length with 50. 0:43 This 90 goes for the angle, it replaces every angle with 90. 0:47 That's how it works, okay. 0:49 So let's go back real quick and simply run this now. 0:54 Okay, so I'm gonna hit the shortcut key to run it. 0:59 And you can see I said draw two squares and it did. 1:03 But, here is the most amazing concept in programming, 1:09 which is the concept of doing things over and over again, 1:12 also known as loops. 1:14 So if I said I want you to do 10 pushups, 1:19 that's like a loop. 1:22 And every time you do a pushup 1:23 I count one, two, three, four. 1:25 And then once you hit 10 I stop automatically. 1:28 So a way to say that here is you can say 1:32 for pushup in range 10. 1:35 So for each pushup for 10 times, do this. 1:40 And this pushup part, I can call it whatever I want. 1:42 I can call it this, 1:44 I can call it I, 1:46 we'll just keep it simple and leave it at one letter I. 1:50 And what we're gonna do is, 1:52 all this part says is run something 10 times, okay. 1:58 That's what that part essentially says. 2:01 If I run that code on the left hand side, 2:03 if I show you what a range of 10 gives me, 2:05 it gives me this. 2:07 So when I do range 10 it won't really show you, 2:10 it kinda hides what it gives you, 2:12 but in reality it gives you a list of 10 numbers, okay. 2:17 So we're gonna talk about more things like lists 2:20 and integers and floating points in our next video. 2:23 But for now, I just want you to think of it 2:26 like it gives us 10 things and so it runs 10 times. 2:30 Okay, so if I did for I in range 10, 2:35 and I said print I, 2:39 what actually happens is the first time in this list, 2:42 the first time you run through in this loop, 2:45 I is zero. 2:46 Then the next time, 2:48 this range 10 is really this list here, 2:52 so I is zero the first time then it's one, 2:55 then it's two, then it's three, then it's four. 2:57 And each time what happens in the loop 2:59 is the part that's indented inside of the loop, 3:02 that's the part that runs over and over and over again. 3:06 So what happens the first time I is zero, 3:08 we say print zero and we get the zero right here. 3:11 Then we say I is one, so I is one over here, 3:14 and then it says print one, we get one over here. 3:18 Then in the last one, I turns out to be nine, 3:21 so we print nine and then we get this nine over here. 3:25 Okay, that's the basic idea of how the loop works. 3:29 So the part that we want to run over and over again, 3:34 we're going to put it inside of this loop. 3:36 Notice the colon at the end, very important. 3:39 And I'm gonna put this part inside of the loop. 3:42 And I don't even need to put that, 3:44 I can just do this 3:48 and I'm basically saying, 3:49 do this thing here, draw a square, four times. 3:53 That's all I'm saying, okay. 3:55 And I will replace this code in that regular way 3:59 without a loop and I'll prove it to you. 4:00 So first let's run it like this. 4:08 Dang, that was cool, right? 4:11 That was really frickin cool. 4:13 It just ran that four times in a row. 4:15 Now, I can show you what I mean, okay, 4:21 and I'm gonna comment out these lines. 4:26 And you can see it's gonna draw that 4:28 same four squares that we just drew, okay, just like that. 4:32 But by using a loop, your code gets a lot more clear. 4:37 What if you didn't want to run it four times? 4:38 What if you wanted to run it one million times, yeah? 4:42 It would be a lot harder to write 4:44 that out one million times, 4:45 but it's really easy to write one million in here. 4:48 I think that's one million. 4:50 That's 10, 100, 1000, 4:54 10,000, 100,000, 4:56 1,000,000. That's actually 10 million. 4:59 So there you go, 10 million. 5:02 So this thing is gonna run 10 million times. 5:05 If I ran it, and I'm gonna close it really quickly 5:08 cause this is gonna keep running forever, 5:10 but you'll notice that it just keeps overlapping 5:13 on the same square and it's gonna do that 5:15 10 million times so if I went to sleep 5:17 and woke up this will probably still be happening 5:20 and then it'll still be happening after that. 5:23 So let's exit that before something crazy happens. 5:29 Okay, so that's loops for you guys. 5:33 That is it for this video, 5:35 I will see you in the next video.

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