WEBVTT

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>> Hello everyone and
welcome to intro to

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Python here on
Cybrary on demand.

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I am your instructor Joe Perry

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and you are watching Lesson 9,

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the final lesson of this class
in which we are going to

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be doing a deep dive on
Python dictionaries.

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Just like with the last lesson,

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we only really have
two objectives here.

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We're going to learn the
key dictionary methods,

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and we're going to learn to
make use of dictionaries.

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We talked about dictionaries
very briefly in Module 1.

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We haven't really dug into

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them the way they
deserve to be dug into

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because dictionaries
are incredible.

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You can do so much with them.

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They're just these
ridiculously useful tools.

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We're going to really
dig into those.

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We're going to spend some time

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on them here in this lesson.

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First, just like
we did with lists,

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we're going to create
our first dictionary

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which we're going
to call dict_one.

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Actually we could do
underscore what the word one.

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We're just going to

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assign a couple of
simple key-value pairs.

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Remember that as
we do with lists,

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we can address inside
of dictionaries.

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But instead of using
indexes, we use the key.

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Note that you can't
reverse that.

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You can't use the
value to find the key,

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it has to be the key
to find the value.

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Anytime you give a
dictionary a bad key,

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it'll spit out a key error
and it's just going to

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tell you whatever you
used was not valid.

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Just like we did with lists
and strings and numbers,

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let's do a dir against

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that dictionary and see
what things are available.

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Now, it's a shorter
list than it were for

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strings because you can do
crazy amount with strings.

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But here you see
we've got clear copy

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from keys, get items,

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keys pop, pop items, set,

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default, update and values.

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The ones that I really want
to look at, first of all,

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let's look at dict_one.keys.

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Here you can see this
is a built-in method.

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That means that it's a function.

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We can address it.
You see it's going to

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spit out this list right
here of 1, 3, and 5.

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Dict keys is basically just,

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I'm not going to dig too far

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into exactly what that means,

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but essentially
it's an iterable,

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it's something that
you can address.

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For example, you could do
something like for i in

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dict_one.keys, print i.

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What this is going to
do is it's going to get

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back essentially list of keys.

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It's going to go through key by

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key printing the
values associated.

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Here you can see that
we print 2, 4,and 6.

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That's one of the really
useful things you can do

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with dictionaries is
get all of the keys

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back and print all of the
values if we wanted to.

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This is a slightly
advanced use of for loops,

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but I'll show you for
k, v in dict_one.

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keys. Actually I'm
going to do that

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>> slightly differently.

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>> For k in dict_one.

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keys. [NOISE] Print,

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format, k, dict_one.

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That's a slightly complex

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function that we
just wrote there.

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What we're doing is
we have these two.

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Remember our brackets from
our discussion of strings.

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We're using Format,

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and we're saying the first
item to insert is the key.

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The second item to insert
is the value that we

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find by looking it up
in our dictionary.

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[NOISE] You see here
that it will print 1,

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2, 3, 4, 5, 6.

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That's an easy way
to find all of

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the associated keys and
values in a dictionary,

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Now let's look back at our list

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of functions for dict_one.

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We see that we
talked about keys.

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We also have pop here,

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and pop is a little
bit different in

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a dictionary than
it is in a list.

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To see that we're going to

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go ahead and we're
going to do help.

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[NOISE] You see that

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you have the argument here of k

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and an optional argument

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of d we're not going
to address right now.

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Then it's going to return v. It

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removes the specified key

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the same way we did
with pop and lists,

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and instead of giving
you back that key,

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it gives you back the
corresponding value.

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I'll show you, [NOISE]

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and we'll give it
the key of five.

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It printed six. Now if we look
at the dictionary itself,

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we see that it no longer
contains that key value pair.

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That's a little bit different
because you're actually

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popping with a specific argument

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telling it which key to take.

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It's not just taking
the last item,

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it's taking a specific key,

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and it's removing that
key and the value from

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your dictionary
and it's printing

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or returning back to that value.

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That's the general
concept to dictionaries.

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The uses that you're going
to get out of these,

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there's so many potential
use cases for dictionaries.

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You can associate
data with them.

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You can get access to
all of the functions,

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all the methodologies
inside of them.

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In our lab, which is going to be

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coming up right after the
summary and review video,

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you get a chance to
really play around with

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dictionaries and see all
the different uses of them.

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But I wanted to show you just
again how to create them,

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how to address them, how to
find the methods of them.

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They are just these remarkable

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tools that I absolutely love.

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I get really excited
talking about them.

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In this video, like
I said, we talked

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about the key
dictionary methods,

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and then we discussed the
different uses of dictionaries.

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In your supplemental materials

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you'll get to do a
lot more of that.

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If you've finished this video,

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you're about ready to do
our summary and review and

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then our final lab and
our final assessment.

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I just want to thank you for

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being here with me
through all of this,

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and I'll get a little bit sappy

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about it in our next video,

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but just thank you so very
much for watching this.

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I is always have been
your instructor,

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Joe Perry, and you've
been watching,

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you've completed your
last lesson of intro

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to Python here on
Cybrary on demand.