Variables

Quick reference

• 00:04 In this video I want to talk about variables and
• 00:07 variables are just very important to all programming.
• 00:10 They're sort of a fundamental thing.
• 00:11 You're always going to have them, you're always going to use them.
• 00:14 And a variable is basically a bucket.
• 00:16 It's a container, it holds something and it generally holds one thing.
• 00:20 You can put different things in over time.
• 00:22 You could put something in and then take it out, and put something else in, but
• 00:26 it's just very important and creating a variable on Python is super easy.
• 00:30 You don't have to declare it, you don't have to do anything except just name it,
• 00:35 and so lets create a variable called first_name.
• 00:39 Now, we have a variable and to put something in it we just put an equal sign,
• 00:43 this is called an assignment operator, and
• 00:45 then quotation marks and I'm going to type John.
• 00:47 So this is actually a string, and we're going to talk about strings
• 00:50 in a little bit, but you can use single quotes or double quotes,
• 00:55 and there's a reason to use either one of those.
• 00:57 We'll talk about that later too, not really important at the moment.
• 01:01 But now we have assigned John into the variable first_name.
• 01:05 So if we save this and run our program, you see nothing happens.
• 01:09 Because we've created a variable, but we haven't actually done anything with it.
• 01:13 So if we want to say print this to the screen, we just type in the variable.
• 01:18 And you can see as I start to type this out,
• 01:20 our text editor here already knows what we're trying to do.
• 01:24 So you can click on this or you can hit your tab key and
• 01:27 it will auto fill it in for you, which is really nice.
• 01:29 So if we save this,
• 01:30 come back and run it again, we see it prints out John to the screen.
• 01:34 So that's really, really cool.
• 01:36 So like I said, you can could put stuff in variables, they're like a bucket,
• 01:38 they're a container.
• 01:39 You could put strings of text, you could put numbers and
• 01:42 we're going to talk about numbers in a bit.
• 01:44 We could say, my_fav_number = 41.
• 01:49 And notice, this number does not have a quotation marks around and
• 01:53 there's a reason for that, strings have quotation marks numbers do not,
• 01:56 they're a different data type.
• 01:57 And we'll talk about data types in a couple of videos from now,
• 02:00 but those are variables.
• 02:01 Now, a couple of things, when you're naming your variable first off,
• 02:04 it's important to name your variable in a descriptive way.
• 02:08 In this case, we're going to be putting a first name in here.
• 02:11 So I named the variable first name that sort of makes sense.
• 02:14 If you're going to put somebody's age, you might name your variable age.
• 02:17 Now, whatever you're trying to do, be descriptive.
• 02:20 That's very helpful.
• 02:21 The next thing to notice is
• 02:22 variables have to be one word.
• 02:24 And you see this is two words, but it's all connected.
• 02:27 We could not have first and then space, that's invalid.
• 02:32 You see we get this angry x that says invalid.
• 02:36 So you need to, when you using multiple words like that use an underscore.
• 02:40 Now, variable names can only be characters, letters,
• 02:45 underscore or numbers.
• 02:47 But you can't start your variable with a number so we couldn't say like
• 02:52 1_first_ name, we get this angry x, that's invalid.
• 02:57 Also variable names are case sensitive.
• 02:59 So here we have lowercase f, lowercase m.
• 03:02 We could go First_Name, let's just change it to Tim.
• 03:08 Now, these are two very separate variables.
• 03:11 They're completely different because Python is case sensitive.
• 03:14 It sees this uppercase F and uppercase N, it says okay,
• 03:18 this is a different variable than this one.
• 03:20 So keep that in mind.
• 03:22 Generally speaking, you don't want to use uppercase letters for the first word.
• 03:27 Generally those are reserved for classes, you can get away with it but
• 03:29 it's not a good thing to do.
• 03:31 Also, we use these underscores.
• 03:33 Some people use camel case, and that's like first and then capital Name,
• 03:37 and we call this camel case because there's like a hump in the middle,
• 03:41 this uppercase is like a camel has a hump.
• 03:43 Now, this is popular in a lot of programming languages,
• 03:46 JavaScript is like this, you can do this in Python but I don't recommend it,
• 03:51 sort of the convention is to use an underscore, sort of a personal preference
• 03:55 but the Python community tends to use this underscore instead of camel case.
• 03:59 So those are some rules for naming variables.
• 04:03 Like I said, we can change these over time.
• 04:05 So if I come back here and go first_name = "tim" and
• 04:10 then print(first_name), if I save this and
• 04:15 run it it's going to be John, and then Tim.
• 04:19 because the first time it's John, and then we changed it to Tim, and
• 04:23 printed it out the second time, and so now it becomes Tim.
• 04:26 So you can change them over time, you can add things in, you can take things out.
• 04:30 We can remove anything, save this and run it.
• 04:33 We get John and nothing, so like I said variables you're going to use them
• 04:37 forever, they're a fundamental part of all programming doesn't matter what
• 04:40 programming language you'll use they all have variables and very handy.
• 04:43 So in the next video we're going to look at data types.

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