Python Programming Tutorial #6 - For Loops

Key Takeaways

Hey guys, welcome back to another video. This is the sixth video in my Python programming series and today we're going to be talking about four loops. Again, if you missed the other videos in the series, please go back and watch them first as it's going to be hard to understand if you haven't seen them already. Okay, so let's get right into it. Today we're going to be talking about for loops. Um, and a loop is a new thing now if you're a beginner in Python. And I'll talk about how they work. We're going to start off by just writing one out. um getting right into it with the syntax. So for x in range and then we're going to put a number which is going to be our starting position. So in this case I'm going to put zero. Um and then a stop point. So 10. Okay. And then we're simply going to print out x. Now I know we did this pretty quickly but let's talk about what this is and the syntax. So a for loop is going to run a certain amount of times. So in this case, we're going to start at zero and we're going to go to 10. This means the for loop is actually going to run 10 times. So what's going to happen is we are going to have our variable x which is right here. And every time the for loop runs, x is going to be increased by one. Now we can increase it by more if we'd like to by adding another comma here, but by default it is set to one like this. I've just put it in so that you can visualize it. So really, we have something start, a stop, oops, stop, and an end. Start, stop, step. Sorry, my bad. I'll just put commas here to show you how it works. So you can see we have our zero. That's our starting number. Our stop, which is 10, and our step, which is going to be one. So I know you don't quite understand yet, but you will after I show you a few examples. So we have x is our variable which is going to be holding the number um of what iteration we are through. Now iteration uh just means how many times we've already looped through this loop. Okay. So let's uh do an example here. All right. So we have x and we've just started running this for loop. Now right now x is zero. We're going to print x. We're going to print zero to the screen and then we're going to add one to x. Now this time we come through the loop we say well is x less than 10? Yes it is. So now we're going to print x. x is one. Now we're adding um two. Okay. So now x is 2. Is 2 less than 10? Yes. 2 is less than 10. So let's print two. Okay. And we keep going until eventually we print n. Then x has one added to it. So it becomes 10. Well 10 is not less than 10. So we're not going to print out 10. All right. All right, I know I just talked a lot there, but let's see it in action. All right, so just like I said, we print out the numbers 0 through 9. Now, this may seem weird um because I have the value 10 here. So, you'd say, well, why doesn't it print out 10? It's because of the way the loop works. So, like I said, really what's happening here is this um plus equals 1. So, pretty much this means we're just adding one to the variable x. Um you can also write it like this. X= X + 1 like that. All right. So we print out X and then we add 1 to X and we have to be less than 10 for this loop to run. So on the 9th iteration we have well 9 is equal to 9 + 1. So X is equal to 9 + 1. Uh we get the value 10. Now again 10 is not less than 10. So we are not going to print out 10. Um yeah. So, that's pretty much how a for loop works. Um, it's pretty basic. This is the syntax. We have four and then a variable name. So, this doesn't have to be x. We could use anything we'd like to use. Could use hello. I could use um any other word. It could be as long as I want, as short as I want, doesn't matter. Um, then we have the word in, which is highlighted in orange. And then range. Now, the range takes a different amount of arguments. pretty much an argument is whatever's inside this brackets. So like at the beginning how I showed you we just did zero and 10. This means we have a start and we have a stop. So we start at zero and we go to 10. Now I can also I can actually put one argument in here like this 10. And that just means that we just have a stop. So by default Python will say well we're just going to start at zero and we're going to step by one. Now I haven't showed you the step yet. So we'll do that. Um, so again, we're going to start at zero. We're going to stop at 10. And we're going to step this time by two. Now, what step is is how much we add to x every time. So before I showed you we had x = x + 1. Um, in this case, since the step is 2, it's going to be by two like that. Okay. Um, so let's go ahead. Let's run this. We have 0 2 4 6 8. And you notice how we again do not print out 10 because 10 is not less than 10. Okay. Again, uh we'll do another example with the step. Let's put five in this time. Now you can guess what's going to happen. 0 five. It actually only prints out two things because we start at zero. So we print zero. And then we add five. We get five. Now 5 + 5 again is not less than 10. So we are not going to print out 10. Okay. So, that is the tutorial on the for loop. We're going to do another type of for loop where we're going to use something called a list a little bit later on, but right now we're just using this one. This is the basic one. I encourage you to play around with it yourself. Um, and yeah, so if you like the video, please go ahead and like it and subscribe, and I will see you again for another video. Thanks. Goodbye.