WEBVTT

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Another type of loop is called a while loop.

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A while loop runs as long as a condition is true.

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Be careful.

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If the condition never becomes false, it will run forever.

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Okay, so please pay attention to this.

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We have an example.

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Count equals to five while count greater than zero.

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Go and print count.

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And here we need to decrease count by one.

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Because if we remove this line it will run forever.

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Because five is always greater than zero.

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And this condition is always true.

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And we are going to loop for infinity and make our computer crashes, make, uh, and make the system

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blocks or uh, the application not responding.

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So please pay attention.

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This is a very important thing we need to pay attention for while count greater than zero.

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Go and execute print count.

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Go and print the count value and decrease with every iteration the count by one.

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Let's run the cell count five, four, three, two, one and blast off.

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Okay, so we exit this loop and execute this line whenever the loop finish executing okay.

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Also we can introduce the else statement with while so here else print.

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For example count is no longer than zero.

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Let me run 54321.

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And with the else statement we can run a block of code once when the condition no longer is true.

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So here zero greater than zero no go and execute the else statement by printing count is no longer than

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zero.

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Okay, so we can use the else statement with the for and with the while loop.

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Okay, this is a very good example.

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Another example.

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Keep asking until the user types quit.

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So we have this command which is a string variable.

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Empty string variable.

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While command dot lower doesn't equal to quit command input, enter a word or quit to exit.

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If command equals to quit, go and type for you typed command.

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Otherwise go and make goodbye.

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Okay.

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Enter a word or quit.

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To exit any word like this.

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Click enter.

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You typed this another way.

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Alice.

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Let me type here.

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Alice, you typed Alice.

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You keep, uh, printing the input until you put quit.

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Click quit, and you can notice that the program quits and display a goodbye message.