The second type of Python loops is wild. But what is the difference between four and while loops? Well, unlike a for loop, which executes a code block a number of times, depending on the sequence it iterates over a while loop executes a piece of code, as long as the user defined condition is evaluated as true. If the specified condition does not change, meaning it doesn't become false, then the while loop will continue running forever, and we end up with an infinite loop. When the condition becomes false. Python continues to execute the code following the while loop, if any.

Now let's see an example of a while loop. For this we will create a new file called Wild dot p y. Now let's open up the file in Notepad plus plus. First we should create a variable X with a value of one so let's say x equals one to create a while loop. You have to type in the wild keyword, followed by the condition you want to evaluate and then a colon. So let's say while x is less than or equal to 10 colon, below using the tab key for indentation, you will specify the code to be executed as long as the condition is evaluated as true.

So let's say print x, and I will add x equals x plus one. And I will explain this shortly. For now let's just save the file and run it in the windows command line. So CMD let's move this over. And now let's say Python, D, colon backslash wild.pi. And the result is the integers from one to 10 printed out on the screen.

So let me explain what just happened. Python takes the first value of x which is one initially evaluates it against the actual Less than or equal to 10 condition as true, prints x to the screen and then increments it by one. Now, X being equal to two, it is again compared to 10. And the result is again true, then it is printed out on the screen, and incremented once again, and so on until x reaches 10. Now, having x equals to 10, the condition is still true, because 10 is less than or equal to 10. That's why 10 is also printed out on the screen.

And it is then being incremented to 11. Now, when evaluating the expression 11 less than or equal to 10, Python returns false and exits the loop without printing anything or incrementing the value of x. But what would happen if we don't specify the statement that increments x? This x equals x plus one right here. Well, x is initially equal to one during the first iteration of this loop. It is compared to 10.

And the expression returns true. So it is then passed to the code below the wild statement, it is printed out on the screen. But this time there isn't any statement to increment it. Let's delete this by the way, so it keeps its value of one for the next iteration. That's why it is again compared to 10. The condition being met once again, the same scenario will repeat over and over again forever.

That's called an infinite loop. And you should always avoid ending up with such a scenario in your programs. So let's test this because we already know we are going to generate an infinite loop. Remember to use Ctrl C to interrupt the infinite loop. So let's save the file as it is. And let's run it again in the windows command line.

As you can see, one is being continuously printed out to the screen to interrupt this infinite loop control C and we get a keyboard interrupt and the program is aborted. Another way to work with while loops is by using an expression which always evaluates as true in order to make Python to something over and over again until you tell it to quit. A great example would be an interactive menu, where the user can select a value and execute a piece of code, then return to the main menu and so on. The way to do this is by simply using wild true, which makes sure that the expression is always evaluated as true, the syntax for this would be wild true, and that they do something. We will see such an example later in the course. So don't worry.

One last thing on while loops is that we can use the else statement again, this time with a different meaning. The indented code below the else clause will be executed only when the condition specified in the wild statement becomes false. So let's see an example of this and tested. Let's add the old statement again, x equals x plus one And let's add the else clause at the same indentation level as the while statement. So else colon. Now using the tab key print, let's say x is now greater than 10.

Let's save the file, and let's run it once again. So using the same example, as earlier, Python prints out x on the screen, as long as it is less than or equal to 10. When x becomes 11, and the condition in the while statement becomes false, the code below the else clause is executed. So we get this x is now greater than 10 string printed out on the screen. Pretty cool, I think very useful stuff. Now, often, you will see for loops within other for loops.

Same thing with if and while statements. You will also need to use if statements inside for loops or while loops depending on what you're trying to achieve in your programs. Next we're going to take a look at this country. structures which are called nested structures. See you in the next lecture.