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String Methods
8:26Let's explore common string methods and discuss where to learn more
So let's start with a string variable.
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It is a quote from Albert Einstein and
it's a great one for
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encouraging exploration here in the REPL.
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So he said a person who never made
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a mistake never tried anything new.
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So there's a built in function that
lets you see the length of a string,
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how many characters it contains.
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It's name is len.
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So we'll play len, and then we'll pass
in our object, our string object.
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We'll play len(quote).
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It has 58 characters, and
that includes spaces.
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So len here, that's a function.
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Remember that everything
you create is an object.
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So our string here that we
created is an object, and
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all objects can have abilities or methods.
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You can think of methods as
functions that belong to an object.
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And you can access methods that an object
owns by using what is known as dot
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notation.
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For instance, there is a great
method on strings called upper.
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It creates a new string,
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where all the characters in the original
string are converted to uppercase.
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It's a good way to make
the computer yell in all caps.
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And I can access the methods
on a specific object,
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so lets use our quote object here by
placing a period after the variable name.
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Now, this period here,
this is why it's called dot notation.
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And now,
I can access the object's methods.
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So that method was upper.
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And it's just like a function.
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So I call it using parenthesis.
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In this particular method,
it doesn't take any extra arguments.
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So we can leave the inside of this empty.
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And there,
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you'll see we returned a new string of
Einstein yelling motivation at you.
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And, again,
note it didn't change the original string,
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and that's because you
can't change a string.
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It returned a new string.
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So as you can imagine,
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there's also a method named
lower that does a similar thing.
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And so, the string owns the method,
lower, and we access it by placing a dot.
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And then, we do the method name,
which was lower, and we call it.
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Which the only character here
that's different is that leading a.
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So this is Einstein
whispering his advice to you.
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Now, if you're heeding his advice,
I'd recommend that you pause me and
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attempt to use a method on
the string called title.
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What it does is it turns all
words in the quote to title case,
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meaning each word has
a capitalized first letter.
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Go ahead and try it.
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Pause me.
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Are you ready?
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Here I go.
This is what I did.
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I did quote, and then I did a dot
to access its methods, title, and
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then I called it.
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So that could be the title of
your autobiography, am I right?
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You can also turn most objects into their
string version using the built in str,
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which is short for string.
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Now, this works the same way
that we coerce strings to ints,
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it's just the reverse, right?
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So we could say str(42), and we'll get
back the string 42, not the integer 42.
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If you're curious to see what
other methods a string owns,
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you can see them by doing help and
an (str).
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So you'll note we have methods defined
here, and they're in alphabetical order.
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Now, these ones that start
with these double underscores,
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these are known as magic methods.
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So let's skip past those for now,
we've got plenty of magic already.
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So, the first keep on pressing
space bar it's jumping.
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So there we go.
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I think I saw the first one
outside of there is capitalized.
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So here,
this capitol S represents our string.
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And you can see it's
calling capitalize with no
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arguments because it doesn't take any.
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And it returns a new string.
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That's what this arrow means,
it means it will return you a new string.
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And the instructions of what it says is it
will return a capitalized version of S and
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make the first character have
upper-case and the rest lower-case,
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which our string already does.
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Now please,
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don't feel like you should be able to
read all this documentation right now.
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We'll get there, but you should be
starting to recognize some words and
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concepts.
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Just like foreign language immersion.
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Isn't that kind of cool?
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Now unfortunately, most documentation is
not written with a beginner in mind, and
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some terms and
knowledge are taken for granted.
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But hey,
that's what we're here for, right?
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We'll get you reading this type
of documentation in no time.
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Keep immersing yourselves.
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Okay, now press Q to drop out
of the help documentation.
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And I'd like to show off a pretty
handy feature of strings that you'll
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use quite a bit.
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It's called string formatting,
and it allows you to create
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a reusable template that can be
populated with different data.
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Think of these kind of like a mail merge.
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For instance, let's build one for
an e-mail subject for treehouse students.
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The e-mail subject when populated would
probably look something like this.
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We'll say thanks for learning JavaScript
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with us Craig.
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That's just one of the topics
that we teach is JavaScript.
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So what we could do is we could
define a template just like this for
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all topics and for all students.
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And all we would have to do is
just switch out the variable.
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So what you do is you create a variable.
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We'll call it subject_template, and
we'll make it so we can reuse this later.
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And now, this could be named anything,
don't worry about subject_template.
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And what happens is you put your
string that you want your template.
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So we say thanks for learning.
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And then, when you want to replace
something, you add a placeholder.
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And those look like this.
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It's an open curly bracket and
then a closed curly bracket.
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So Thanks for learning { } with us.
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And then,
we're going to also change the name out.
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We're going to put another placeholder.
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So we'll do an { } and we'll do an !.
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Close that.
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So now that we have a template,
we can fill it with data.
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So we're going to use
the format method on strings.
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It is a method that they own.
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subject_template.format.
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And the way that this works is you put
in the first parameter, we'll replace
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the first place holder and the second one
will replace the second place holder.
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So the first parameter that we want
to push in, we want to say thanks for
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learning Python with us.
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And so, Python is the topic.
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And Valentina is the name
that we'll use here.
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Thanks for
learning Python with us Valentina!
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Awesome, right?
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And you can keep using different strings,
right?
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So here, we also teach Java.
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Somebody that I appreciate
on our team here.
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We have Thanks for
learning Java with us Shadd.
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Awesome, right?
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Now, numbers will
automatically be coerced.
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For instance,
if we had a purchasing screen,
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like something said you just bought,
and then we put a placeholder for
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a number of items, and then we put
a placeholder for what the item was.
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So we say you just bought,
now we'll do .format,
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and we can pass in 3 and fidget cubes.
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And there,
you see you just bought 3 fidget cubes.
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See how the 3 was automatically
coerced to a string?
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But wait, there's more.
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One more powerful feature of strings
is that you can check to see if
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one string is contained in another.
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Now, you can do this with the keyword in.
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It ends up reading very clear.
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So for instance, if you want to see is
there ham in hamster, It returned true.
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This is saying that this expression
is true with a capital T.
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It is true that the word
ham is actually in hamster.
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And the reverse is also true.
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Is the word popcorn in hamster.
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It's false.
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And you can see that, right?
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It's returned us back
a False with a capital F.
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Now, these true and
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false values are actually a different
data type that we should explore.
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These are called Booleans.
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It's true that we're about to
tie up this string exploration.
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So take a quick break and then come back
refreshed ready to dive into Booleans.
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