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Let's talk about strings.

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Strings are a thing called a sequence.

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So a sequence is really just a generic term for an ordered

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set. That means you have a list of things to work off.

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And so when we said, let's not do 'name', let's do 'courses

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= "Python

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for Everybody", this is called a string.

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And so if we run 'type', not string, 'type(course)',

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this will just say string, 'str'.

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But behind the scenes, Python is ripping this apart.

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It is saying, there's a P-y-t-h-o-n, space, f-o-r, space,

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E-v-e-r-y-b-o-d-y, and it is trying to map all of it.

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Now, before we get into the sequence of a string, let's actually

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break down what a string is.

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A string really is just a sentence.

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So let me actually write that out.

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A "string" is just a sentence.

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That's all it is.

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It can have spaces,

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it can have commas, underscores, special characters,

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uppercase, lowercase,

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it can have pretty much anything as long as it starts with

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one of three things.

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A string needs to start with quotation marks.

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It needs to start with either quotation marks, or apostrophes,

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or a set of three quotation marks, or three apostrophes, like

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this. Now, there are different reasons for using these, and

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let's explore some of them right now.

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So let's say I have a sentence, a 'sentence', and it says,

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"What's going on?"

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And when I display the 'sentence', it says, "What's going on?". Not a

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problem. But we can also create this sentence with apostrophes

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instead of quotation marks.

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Now you can actually see the syntax highlighting here is

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broken, and that's because Python says, "Oh, you're starting

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with an apostrophe?

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This whole thing is going to be a string, and I'm going to keep

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thinking that it's a string until it matches the next apostrophe.

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Now, we, as humans said, well, the last one should be over here,

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but because this is a, I think it's called a conjugated

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word, it has an apostrophe right in here.

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And instead of saying, "What is", we said, "What's",

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and this is going to break. 'invalid syntax', Python is actually

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telling us exactly what it is. It's a 'SyntaxError'.

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So what we can do here is use quotation marks instead, and that works.

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And that continues to work.

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We could also use three quotation marks or three apostrophes,

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either one here is going to work.

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So if I keep running these cells, you're going to see that

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nothing actually changes and it continues to work.

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Now, the thing that I was getting at before is, if I just

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copy this over and get rid of those, that's 'SyntaxError',

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because we're using the same quotations.

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Well, sometimes it's not super easy to just change your quotations,

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or your apostrophes to quotation marks, or to a thing called

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the Docstring, which is the three in a row.

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But what we can do is we can say, "Hey, Python, this one in

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here, right here, is not actually the end of the string".

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And we tell it that it's not the end of the string,

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and to render it as a regular character by adding a slash, '\'

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in front of it, and this is called escaping.

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So Python now sees "\'", and says, "Okay, well,

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when I render this, I'm going to make sure that "\'"

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shows up as just a regular apostrophe.

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So let's go ahead and and run this as well,

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and it works.

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Now, sometimes you're going to want a string or a sentence

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on multiple lines.

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That's a fairly common thing that you're going to see in

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Python. And there are a few different ways we could do this.

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We could say 'course = "Python", and we put that in a string,

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so starting and ending with quotations, then we add a slash,

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backslash, '\', and then on a new line, we could say, "for Everybody",

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and let's run this.

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And we can actually see that it put it all in one line because

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I didn't do the spacing properly in there. There we go.

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I needed that extra space inside of the string for it to

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basically say, "Hey, there's one here, and there's one here,

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but because they're on two different lines followed by this

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little slash, '\' in the middle, put them together.

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So that's one method of doing it. Another method would be

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to use parentheses. So we could use an opening and closing

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parentheses here.

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And so let's say "Hello", make sure we add spaces this time,

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"My name is", "Kalob".

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Let's run that, and let's not call that 'course',

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let's call that 'greeting', because that's not a course,

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and that's just a terrible way to improperly name variables.

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And so let's run 'greeting' in here, and we see, "Hello.

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My name is Kalob".

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So that's the second way, is with parentheses.

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And because there's an opening and a closing bracket in here,

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Python is automatically going to say, "Okay. Well, I understand

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what you're trying to get out here." So you don't need to

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have the slash in there.

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It's just going to understand that this is a string, beside

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a string, beside a string, and just puts them all together.

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And when Python puts things together like that, when it puts

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a string together with another string, with another string

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just like this, that's called concatenation. concatenation.

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Now there's one more way, and you're going to see this one a

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lot in the wild,

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and this is more of a thing called the Docstring.

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So let's actually call this a 'doctstring', 'docstring', and

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it is equal to three opening quotation marks, """ or three opening

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apostrophes,''', it can be either one, and it has to end the

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same way, too. That's important.

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Whatever it starts with, it needs to end with """Hello.

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"this", "is", "a", "docstring".

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And we're going to see something a little different with this one.

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"docstring"

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Let's go ahead and run that.

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And if I do,

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I didn't name that right either,

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[no audio]

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And I also typoed that one. Look at that.

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At least I'm consistent with my typos.

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And if I put 'docstring' in here and run it, you have these

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things with a '\n'.

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Now, in programming, you can make newlines like this,

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and you can have it displayed out.

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And whenever you see a newline, and actually you see it

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a lot in any code, any text editor, any website, you see

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newlines all over the place.

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This '\n' is a newline.

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That's what it means.

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It's called an invisible character, and it doesn't actually show up.

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But whenever a computer recognizes that there's a '\n',

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it says, "Oh, okay. Well, let's put that on a new line".

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And that's what this did here.

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So it said, "The docstring started,

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and then there was a newline.

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"Hello", newline,

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"this", newline, "is", newline,

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"a", newline, "docstring", newline.

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But because we just wanted this as a regular string, it said,

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"Hey, just so you know, there are supposed to be newlines in here".

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Now, what would happen if we were to print the 'docstring'?

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Instead of just displaying what the value is, let's actually

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print the value of 'docstring'.

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Look at that, 'print', the function

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'print' looks for '\n',

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and says, "Oh, there's a newline".

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"Hello", there's a newline.

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'this', there's a newline.

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And it continues to go on and actually creates newlines for us.

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Now, if you're just jumping into this video, and you haven't

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watched the previous videos, a fun little fact about strings

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is they are immutable,

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that means they cannot be changed.

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All we can do is overwrite the variable name with a new value.

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Now, I mentioned that this is a sequence, and a sequence

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is basically a generic term for, like, an ordered set, like a grocery list.

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And so what we can do here, and this is getting a little

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advanced, so you don't have to know this part,

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but I'm going to demonstrate this.

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Let's do 'word = "Python"'.

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And let's create a for loop, 'for letter in word',

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and this demonstrates that this is a sequence of letters.

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This isn't just one word called "Python".

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It's actually six letters, individual letters, according

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to Python's internal workings.

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So we can do 'print(letter)'.

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And what this is going to do is print 'P-y-t-h-o-n.

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Let's go ahead and run that.

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Sure enough, it took every single letter and printed it out

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one by one.

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And that is what makes a string a sequence.