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So there are two kinds of loops you can use in

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Python, the for loop, which you just discovered

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here in the previous lesson, and the while loop,

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which we are going to see now. And you will see

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that the knowledge you got when working on

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conditional statements will be very useful here to

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explain how while loops work, answer's going to

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do the exact same thing. As for the looping, so

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we're going to print Hello with a counter. But

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this time using while, okay, just going to put

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back 10, okay, because that's going to be simpler

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to read. So just follow along, and I'm going to

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explain that, okay. I'm going to do create first

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variable, i is equal to zero, okay. And then I'm

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going to do while i is lower than 10 strictly to

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one and 10. Okay, I put a colon, and then I do

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print, Hello, and then plus str(i). Okay, so let's

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print the same thing. And I do i plus equal one.

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Let's actually comment, those two lines. Ok. So as

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you can see just comment, like this, so those

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will not be executed. I'm running the program,

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and you can see we have Hello 0 until Hello

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9. So this is the exact same behavior with

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this, and with this, we have the same behavior. So

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now how does it work? Well, the while loop is

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different here, because we have the while, you are

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going to test here, this is a conditional

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statement. Okay. So the while loop is basically

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the same as if structure. The difference is that

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while this condition is true, this block of code

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will continue to be executed. Okay. So you check

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if that is true, it is true, yes. Then you execute this.

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You come back to line five, you check again if

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this is true, if yes, you continue to execute

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this, etc, etc. And then when we come back to the

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line five, and if this condition is false, in that

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case, we don't enter the block of code and rerun

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the program here at line eight. So what did I do

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here, I created first variable i that we're going

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to use as a counter. Now I'm going to check while

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i is strictly lower than 10. We continue to execute

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this. So at first i is equal to zero. So is zero

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is lower than 10. Yes, we print Hello plus zero.

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And then what I'm going to do, I need to do that,

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I'm going to add one to counter. Okay, so I'm

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going to add one every time. To add one, so you can

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actually do i is equal to i plus one, okay. But

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there is a shortcut, you can do plus equal and

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this is simply going to add the element on the

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right to the variable on the left. So now i is

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equal to one, I come back to line five, one is

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strictly lower then 10, yes, we bring Hello one,

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and then i put plus one, so i is not equal to two,

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etc, etc. At one point, i will be equal to nine.

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So nine is lower strictly lower than 10. Yes, we

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print Hello nine, I do nine plus one. So we get

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10. No, i is equal to 10. We come back to line

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five and then is 10 strictly lower than 10. No,

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this is false. So we stopped the while loop. Okay,

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and the condition here for the while can be

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anything you want. Okay, here, this is a very

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classic example with a counter. But as an example,

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let's say you read the temperature of your

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computer, okay. And you want to continue doing an

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action while the temperature is lower than the

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threshold. Okay, you continue, you continue, and

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then you continue to read also the temperature.

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And when the temperature starts to get above the

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threshold that you have set, then you stop

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executing the while. Alright, and now that 1

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million dollar question, when do you use for versus

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when to use a while loop. So basically use a

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for loop when you know exactly how many times you

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want to execute an action. Use a while loop when

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you don't know how many times are for example, if

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the condition to continue is external to the loop.

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As an example, let's say you want to ask a user to

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give you some numbers. In the first scenario, you

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want exactly 10 numbers. So you are going to use a

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for loop and ask 10 times. In the second scenario,

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you allow the user to give as many numbers as they

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want. And you stop asking whenever the user gives

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you the numbers zero. Here you are going to use a

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while loop. And don't worry if you still have some

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confusion about this. In many cases, both

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options are actually possible, just with a

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different way of writing the code. With a bit of

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experience, the choice will become much easier for

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you. And lastly, if we come back to the example

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here, the exact example I've used here, you can

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see that well here the for loop was actually more

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appropriate because we knew exactly how many times

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we wanted to print the text.