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Let's explore common string methods and discuss where to learn more
Terms
I realize the term object might be a little confusing right now. Everything in Python is an object, so anything that gets created will be one of these objects. Objects can have data attributes, or properties, and methods, or behaviors.
Methods are just functions owned by the object. We will look more at objects as well as how to create and define your own in upcoming courses.
Let the word object roll, loosely translate to the way we use the word thing. This thing here...this object here.
So again, don't worry if it's not completely clear yet, we'll get there!
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So let's start with a string variable.
0:00
It is a quote from Albert Einstein and
it's a great one for
0:03
encouraging exploration here in the REPL.
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So he said a person who never made
0:10
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).
0:32
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.
1:01
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,
1:45
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.
2:40
Are you ready?
2:41
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?
2:52
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).
3:16
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.
3:39
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,
4:09
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
4:14
concepts.
4:18
Just like foreign language immersion.
4:19
Isn't that kind of cool?
4:21
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.
4:27
But hey,
that's what we're here for, right?
4:30
We'll get you reading this type
of documentation in no time.
4:32
Keep immersing yourselves.
4:35
Okay, now press Q to drop out
of the help documentation.
4:37
And I'd like to show off a pretty
handy feature of strings that you'll
4:40
use quite a bit.
4:44
It's called string formatting,
and it allows you to create
4:45
a reusable template that can be
populated with different data.
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Think of these kind of like a mail merge.
4:53
For instance, let's build one for
an e-mail subject for treehouse students.
4:56
The e-mail subject when populated would
probably look something like this.
5:01
We'll say thanks for learning JavaScript
5:04
with us Craig.
5:10
That's just one of the topics
that we teach is JavaScript.
5:12
So what we could do is we could
define a template just like this for
5:14
all topics and for all students.
5:18
And all we would have to do is
just switch out the variable.
5:20
So what you do is you create a variable.
5:23
We'll call it subject_template, and
we'll make it so we can reuse this later.
5:25
And now, this could be named anything,
don't worry about subject_template.
5:31
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.
5:52
We're going to put another placeholder.
5:55
So we'll do an { } and we'll do an !.
5:57
Close that.
6:02
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
6:17
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
6:25
learning Python with us.
6:29
And so, Python is the topic.
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And Valentina is the name
that we'll use here.
6:34
Thanks for
learning Python with us Valentina!
6:38
Awesome, right?
6:41
And you can keep using different strings,
right?
6:42
So here, we also teach Java.
6:44
Somebody that I appreciate
on our team here.
6:47
We have Thanks for
learning Java with us Shadd.
6:52
Awesome, right?
6:54
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
7:02
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?
7:26
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.
7:40
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
8:11
false values are actually a different
data type that we should explore.
8:12
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.
8:21
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