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Welcome to lesson 19 which roughly covers pages 123 to 127 of the automate the boring stuff with life

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on textbook and text is one of the most common forms of data that your programs will handle.

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You already know how to concatenate two string values together with a plus operator but Python can do

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much more than that.

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Let's take a look at some of the ways Python lets you write print and access strings in your code.

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Toping string values in Python code is fairly straightforward.

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They begin and end with a single quote.

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But then how can you use a single quote that's inside of a string.

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For example we have the string that is Alice's cat.

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This doesn't work because Python thinks that the string ends after Alice because of this quote and that

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the rest this s cat is just invalid Python code.

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Fortunately there are multiple ways to type strings.

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Strings can begin and end with double quotes just as they do with single quotes.

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That is Alice's cat.

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One benefit of using double quotes that a string can have a single quote character in it.

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Since the string begins with a double quote Python is smart enough to know that a single quote is just

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part of the string and it's not indicating the end of the string.

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However if you need to use both single quotes and double quotes inside of a string you'll need to use

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escape characters in escape character lets you use characters that are otherwise impossible to put into

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a string escape character consists of a backslash followed by a letter that represents which escape

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character you want to add to the string.

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For example the escape character for a single quote is backslash quote so I could have a string say

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hi to Bob's mother.

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Python knows that since this single quote has a backslash before it.

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This is not a single quote meant to end the string value.

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Instead it's saying put a literal single quote as part of the string table 6 Dash 1 in the automake

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book shows the different types of escape characters you'll use.

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You can have them for single quotes double quotes if you want have a tab or multiple spaces entered

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into your text or if you want to have a new line similar to hitting the enter key.

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Or if you want to have a backslash itself you can just have slash slash.

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So it's trail that newline character.

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Here I'm just going to have something else to print Hello there and then slash in for a newline character

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.

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Are you another new line.

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And then I'm fine escaping that single quote and this so we can have a single print statement.

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Print out text across multiple lines.

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Now if you have text that includes many backslashes that you don't want seen as the beginning of an

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escape character you can use a raw string in Python a raw string is the exact same as a normal string

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except it begins with a lowercase are right before.

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So this is a valid Python string so we can have something like that is

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Karel's cat.

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And because this is a raw string this is literally interpreted as part of the string.

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You can see when it's printed out as a string value.

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Python automatically adds that here let's try copying and pasting this into the print function call

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and you can see right now because this is a raw string.

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The backslashes are literally a part of the string.

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All strings are helpful if you're typing a string value that contains many backslashes and this comes

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up in our lesson in the future about regular expressions.

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Now while you can use slash in to put a new line into a string it's often easier to just use multiline

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strings.

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A multi long string in Python begins and ends with either 3 single quote characters or three double

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quote characters.

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So any quotes tabs or new lines in between the triple quotes are considered part of the string so I

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could have something like.

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Print.

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Begin a new multi line.

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Dear Alice heaves.

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Cat has been arrested for catnapping cat burglary and extortion.

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Sincerely Bob.

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And and that multi-line string no notice.

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I'm kind of breaking the rules of having one instruction per line right here.

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Python's smart enough to realize that.

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OK this is all one quote unquote line of code.

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This is just one function call doesn't matter that it's being split across multiple lines.

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I'm not creating any new blocks or anything like that Python smart enough to know.

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OK until I see another triple quotes.

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Everything here is part of the string including all the new lines.

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So if we stored this string into a variable like spam and we just wanted to display the string content

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inside span Python would automatically format it using the slash Hinz.

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So triple quotes are really handy if you have some gigantic string.

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So I'm going to create a new file editor window and say when to copy and paste the entire text to Shakespeare's

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Romeo and Juliet which I happen to have right here in this text file.

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I can just hit Control ate slept all and Control-C to copy

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and then control V to paste it.

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And now any backslashes or single quotes or new lines that are inside.

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All of this text are just automatically seen as part of the string.

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It's really unlikely that there's going to be a triple double quotes inside of the string and if there

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if there are I can just use the triple single quotes instead.

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I we just end this so all of this is just one giant variable assignment for the span variable.

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And I can just treat that string just like any other string I could print it out.

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That's going to be a lot of output though.

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Let's just print out with the length of this string is just to see roughly how many characters are in

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it.

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I'll save this as example that pi and press 5 to run it.

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OK so that has 174 thousand letters in it.

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Strings use indexes and slices the same way.

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List do you can think of a string like hello world as kind of like a list like value with each character

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being an item in that list.

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So we had something like spam equals Hello world.

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I could do all the same things with strings that I do with lists so I can use indexes to pick out a

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single letter from it.

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I could use slices

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to pick out some substring from it I can use the negative indexes to get the very last character the

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in and not in operators.

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Also work with it.

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So hello in spam would evaluate to true.

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Since this text does exist inside that string

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and see if the letter X appears in that string it doesn't.

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So this evaluates to false.

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And note that this is case sensitive.

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So if I look for capital hello inside that string or turn false.

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To recap strings can begin and end with double quotes just as they do single quotes ASCII characters

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let you put quotes and other characters that are hard to type inside your string code.

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Raw strings will literally print any backslashes in the string and ignore escape characters multi-line

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strings begin and end with triple quotes and they can span multiple lines indexes slices the in and

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not in operators all work with strings just as they do with list