All language subtitles for 12. Python Variables

Now in this lesson, I want to talk to you about Python variables and it's a
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really, really useful concept. But before we get started,
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first I want you to head over to the course resources and get hold of the Day
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1 variables start Repl.it sandbox or you can simply type the URL into the
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browser.
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I want you to first go ahead and fork this starting code so that you can work on
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your own version of it. Now once you've done that,
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then the first thing I want to do is to take a look at this line of code that
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you should have already. And when we run this,
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we should be pretty familiar with what happens, right?
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It will ask us for our name and when we hit enter, nothing happens.
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But behind the scenes,
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this name or this input has now been received by this function.
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But once that's done, it kind of just disappears, right?
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And there's no way for us to be able to refer to it in the future. Or is there?
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Well, this is where variables come in really handy.
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If I give the results of this action a name,
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well then I'll be able to refer to it later on.
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So at the beginning of the line,
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I'm going to call it name and then I'm going to add an equal sign
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and what this does is it assigns whatever it is that the user typed in as the
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input to this prompt to a variable called name.
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So now if I go ahead and run my code again and I enter a name,
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now once I hit enter,
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normally there's no way for me to get hold of this anymore, right?
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But now I can actually go ahead and write print.
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I'm going to print the value of this variable name.
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So now if I run my code and I write a name,
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hit enter,
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you'll see that this gets printed and I can use this at any point in my code
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just by referring to the name that's attached to this value.
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So it's almost like we've saved the data from this action to a name.
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And if you think about it, if you had a phone book, let's say,
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and you just jotted down the numbers of people,
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the next time you look at this,
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there's no way for you to know who's number that is, right?
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In a sense it's the same thing with the computer.
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Even though we've inputted this piece of data,
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there's no way for us to be able to refer to this data unless we give it a name.
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So in our phone book, we might say that this particular number is associated with
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the name James. And in programming we would call this name James a variable.
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So we could write something like James equals and then his phone number.
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And this means that in the future, if we ever need this piece of data,
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we can just refer to it by its name,
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the variable name of James. Now,
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as the name variable suggests,
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it's something that can be changed or can be varied.
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So for example,
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just because this name is set to something up here doesn't mean that I can't
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change it later on. So to make things simple,
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let's go ahead and delete the input function and let's just say name is equal to
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Jack. Print name.
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When I run that Jack is what gets printed inside the console because I'm now
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referring to that piece of data by the variable name.
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But if later on I decide to give this variable a different piece of data to hold
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on to,
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let's say Angela and I print name at this time point after I've changed it,
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what do you think these two lines will print?
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What do you think will first be printed?
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What do you think will be printed second? Let's hit command + enter or control +
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enter and see for ourselves.
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So even though they're both printing the same variable, at this point when we first
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call print, it's holding on to the value of Jack,.
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But by line 5 I've now changed it so that it's holding onto the value of
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Angela.
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This makes it a lot easier when we want to write code like what we did before.
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For example,
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this is the line of code that we had before and we knew that we were going to
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get a piece of data from this input function and then we would calculate a new
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piece of data using the Len function
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and finally we're going to print everything out.
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Instead of having such a long line of code, which can be quite confusing,
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we can, if we wanted to, use variables to store each of these steps.
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So for example,
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we could say that the name was equal to whatever the user inserted as the
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input
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and then when we wanted to calculate the length,
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then we could set that variable to equal the Len function.
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And then inside the parentheses, we'll pass in the name, the value, that's stored
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in the name variable right here. And finally,
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all that we need to do is to print the length,
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like so. So in this case,
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this data is stored under this name and then that data is what's going to be
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used in order to carry out this function
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and then the result will get stored in yet another variable
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and finally that variable will be printed out.
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So let's go ahead and run this code and type in my name.
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So Angela and hit enter and it does exactly the same thing,
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but now we've got all of these pieces of data all associated with a name that we
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can refer to at any later point in our code. Now it's time,
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you guessed it, for a code challenge.
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And I'm going to get you to apply what you've learned.
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So for all of that and more, I'll see you on the next lesson.