All language subtitles for 1. For Loops How and Why

In this lecture I'll explain one of the most important concepts in Python programming, that is for loops.
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I'll use an example, so you not only understand the syntax how to write a for loop, but you'll also understand
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why you should use for loops.
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Let's say we've got these temperatures for Monday so maybe this was recorded in the morning in midday,
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and that in the evening.
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So how can we make a program that prints out the rounded values of each of these values like that?
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So that would be the expected output.
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You can see it down here.
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As you'd get 9 because 9.1 rounded up to the whole number will be 9, and then
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8.8, 9 again.
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And 7.8, 8.
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How can we do that?
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So we need to find a way to access the items of the list and you know a method already how to
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access list items which is using indexes.
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So if you want the first one you use zero.
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So you want to print out the first item, that however would print out 9.1, you want the rounded
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version of nine points one which is maybe you want to look, to have a look at what functions you have
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available.
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Like that.
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So have a quick look here, and you'll be able to find a round.
So round which means you want to round
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a number, so round 9.1, you get 9, and in our case the number we'd like to round up is this
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expression.
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So we want to play round here and in parentheses put that expression.
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So that's number, 9.1.
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So give it a try before rewriting the entire code and that's fine.
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Do that again.
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Write.
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But with 1 and with 2, executes, and you get the expected output, okay, that's fine, it works but what
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if you had a big list of 100 items?
You'd end up with 100 lines of code.
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Well, I can show you how to do that with just two lines of code instead.
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This how you do it. You use a for loop for temperature.
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Just choose a name for a variable for temperature in.
You see how these keywords are highlighted.
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So these are actually Python reserved words.
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Temperature is just a variable.
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That's why it's in black. In Monday temperatures, use a colon.
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And what happens after the colon?
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I told you in the earlier video.
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Well indentation which happens automatically in Visual Studio Code, four spaces.
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What do we want to do for each of the temperatures?
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Well, we want to print out the round form of temperature.
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Just like that, save, execute.
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And this is the output.
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So in just two lines of code we are able to execute some commands for all the items of an array which
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a least in this case, but it can also be a string.
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For example for the letter in "hello", print letter.
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And hello is printed out there.
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And of course you can do whatever you like there, title.
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Get the first item which is the letter.
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So the letter would be capitalized like that.
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So let me go one more time through these two lines to explain them what they mean.
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So what the loop does is for temperature in Monday temperatures.
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So you are creating a variable.
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And what the loop does is it goes through all these items one by one with loops.
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So in the first iteration temperature will be equal,
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so the variable will be equal to 9.1.
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Therefore the round function will round up nine point one and print it out here.
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And if there are more lies in here, for example print "Done".
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If you do that you see if there is another more line like after 9, this line is executed.
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So you get the string "Done" print it out.
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If there are more lines those lines will be executed.
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If there is no more lines, then the execution goes again on the top of the for loop, and the loop gets the
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second item this time.
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So temperature this time will be equal to 8.8 and the same thing happens again, rounded it up,
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print it out.
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"Done" is also printed out, goes to the next line.
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7.6.
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And so one, and then after 7.6 the loop tries to see if there are more items in this array.
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If there are no more items what happens is that this indented block, the execution of this block finishes
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and Python goes to the next two lines to execute what's left in the script.