WEBVTT

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So continuing on with Dictionaries,
I mentioned in a previous video

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after the challenge, there was
a couple of more things to cover.

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Before I start that, I just wanted to let
you know that I've changed to a different

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theme for my videos.

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You can see the background.

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We're now using darcula,
and the reason for

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that is you've probably noticed
in the last few videos,

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whenever a dialogue box Pops up,
the buttons look out of place.

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Because what I've done is I've
increased the font size so

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that you can see these videos easier.

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But there seems to be a bug,
at the moment, in the white background.

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A standard thing that comes with IntelliJ.

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And if I change to this thing,
that problem goes away.

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So we'll see how we go with this color.

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Hopefully it's still good.

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And give me some feedback,
if you wouldn't mind, please, and

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let me know if you're still
being able to see this video.

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And still not very clear on your screen
but certainly good to work with.

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I think I mentioned earlier in the course
when we're installing intellij that I

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actually prefer this for
my everyday development.

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Okay moving on we're going to look at two
more dictionary methods that can be really

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useful in your everyday path in
programming First one is the update method

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and that allows you to combine
two dictionaries together.

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So that's really useful.

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And the second one is the copy
method which is used to

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create a copy of a dictionary.

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And I've created a new file
I've called fruit.pie and

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I've just pasted in our fruit.

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from the original dictionary
videos that we did bout that.

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So I've posted those back in again.

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And we're gonna do,

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what we're gonna do now is we're
gonna store some veggies as well.

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So we're gonna put print fruit.

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Then we're gonna do veg for
veggies equals, let's add some vegetables.

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Cabbage, everyone's favorite.

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Especially children,
every child is maybe not every

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childs favorite

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sprouts, lovely.

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That's debatable I think.

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And spinach,
which is something I actually do like.

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Can I have some more fruit please,

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which would be a typical
response from people to spinach.

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Okay, so we've added three
entries in our dictionary and

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we're just going to
print that out as well.

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We can run that.

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So at the moment Oops, I need to
cancel out of that, so disconnect.

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That does come up and you're wondering
what's going on, it's because challenge is

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selected, which was the last path and file
that was run in this project, so I can

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right-click the current source file run
fruit, and that will then work and then

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subsequently I can come in here and select
fruit or just make sure that's selected.

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But okay, in this example you
can see that we've successfully

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created two dictionaries and
they're separate as you can see.

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One's got fruit and
other has got vegetables.

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So that's working fine.

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But we can actually
combine those together.

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Using the update method, and when we do
that we pass the other one as a parameter.

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So we can do something like
this veg.update(fruit) and

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that's adding the fruit
dictionary to the veg dictionary.

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So we then print that out and run that You
can see now on that third line of output,

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you've got all the entries, and you can
see there we've also got sprouts there.

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Cabbage there, etcetera.

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So we've got both of them combined.

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So that's a really handy command
if you've got two dictionaries and

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you just want to combine them together.

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There of course is nothing
stopping us from also doing this.

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We could have done fruit.update And

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that is added to the fruit dictionary so
I obviously left this example line 13 add

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the veg dictionary to fruit, I am going to
take that again and the entry on line 15,

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of course that is adding
the fruit dictionary To veg.

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Now, the method returns none.

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And if you remember from our
discussions of the list sort method,

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a new list isn't returned when you call
sort, and with dictionary update method,

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a new dictionary is not returned either.

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So, the reason that we've talked about
this and mentioned this a few times

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is primarily for people who are used
to other programming languages and

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may expect a new object to be returned.

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But just to confirm that,
if I do something like this,

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Print is what I'll do,
I'll do at the end here, and then here.

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I can do, print (fruit.update (veg)),

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then I can do print(fruit).

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So we actually run that You see
the first line we got none.

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And the second line you can see
we've clearly got fruit and

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some vegetables in there.

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So, very important to remember
it doesn't return anything.

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You know if you wanted to create a new
dictionary that contained all the items

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say from fruit and veg, but you didn't
wanna modify the original dictionaries.

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Then instead of using update it's a better
option to use the copy method instead.

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So we could do something like this,
we could put,

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nice and nasty equals fruit dot copy.

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And we could do nice and nasty dot update.

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(veg) print (nice and

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nasty) and
just comment some of these lines out, so

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if you run that now, you can see that
clearly there we've done the .copy and

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then the.update and so that last line you
can see were really got 'sprouts' in there

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And fruit, so we've got fruit and
vegetables, so

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let's combine them again, creating
a new dictionary called nice and nasty.

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And fruit and veg, both of those
dictionaries weren't modified at all, and

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so, as confirmation, nice and

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nasty, that dictionary now
contains all the items from both.

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And just to confirm that,
you can do print veg dot fruit.

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And run that.

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And that should confirm.

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You have vegetables on
the second to last line there.

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And it's only vegetables and

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then the last line you can see
scrolling over, that's all fruit.

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There's no vegetables.

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So that's a good way if you wanna copy.

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One example,
one that's gonna be extremely useful.

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What we're gonna do is make some
improvements to the user interface of our

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adventure game.

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So I'm gonna go back to the challenge,
and I'm going to copy all of this.

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We're just gonna create a new folder just
to preserve that source code if you need

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to go back to New > Python,
we'll just call this one game.

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I'm gonna paste that code in again,

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that was the last code from the challenge
That we did in the last video.

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So I think that's something
that would be extremely useful.

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We've gotta change the user
interface of this adventure game.

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And wouldn't it be useful if players
could enter the name of the location

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rather than a direction?

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So I'm still allowing them to go there if
there's an exit from the current location.

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In other words, an account temper
of the map, but for example,

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it would allow them to type hill from the
road instead of west to get to the hill.

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So the easiest way to implement the change
with the current count we've got

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is to extend the vocabulary dictionary
to include the location names.

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So what we're gonna do is extend that.

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So we're still gonna leave
in our other directions.

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But if we then go back in there and
put in So road 1

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and what's this going to be called now?

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Hill 2 building

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3 valley It's gonna be four and

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forest.

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Five.

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But the thing is we can't use
a direction as the value.

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Although Talking road from
the forest moved south

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talking road from the building moved west,
and

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from the valley north so one solution that
keeps maintenance of the exits dictionary

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simple is to use the location number
of street, then For the valley.

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Then we have destination of
one of the exits dictionary.

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We just had another entry one, one so

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we can maintain the exits without
checking the map each time.

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And again, that's easy to see and
to not actually describe.

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So let's go ahead and update that now.

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So what we need to do.

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It's for each location we need to
put in the corresponding number.

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So for number 2 here we've got west 2.

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What we then need to do is put 2:2.

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East will be 3:3,

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North is going to be 5: five and south.

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You guessed it 4:4 then we don't
need to do anything with qui,

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so we'll leave that as it is.

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So likewise for location two,
we need to also put in a five here.

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So five is the key and
five is the location.

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The third one, for west we're going
to put 1, 1 for the location.

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And for location 4 we're gonna do
the same, we're gonna put 1, column 1.

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And the second one after west
we're gonna put 2 column 2,

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we're gonna leave quid in there.

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And on the last line,
we need to put "2": 2.

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"2" being the key, 2 being the location.

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And cuz we're going south,
we also need to add a "1": 1, as well.

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So essentially,
the corresponding direction, we've

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also added that number into it as well, so
that it matches up WIth our vocabulary.

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So, if you go ahead now and
run this, and I'm gonna change this,

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we need to right-click first,
actually, and click run game.

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I think we still should be able
to type in so south, north,

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so we should always be
able to type in valley.

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That takes us to a valley.

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And road,
to take us back to where we were before,

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and we can still get--could still So
that's pretty neat.

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So providing there's an exit tour,

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we're able to type in the destination name
to get there from our current location.

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Now there is actually
an issue with this though.

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So the list of available
exits from a location,

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As you know is built up from the keys of
the exits dictionary for that location.

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So now that we've added the extra
entries to the dictionary,

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we end up with a load of numbers
in the value of x's list.

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And just to run that again, 4352, etc.

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You can see these extra numbers
that are being added there.

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Now we do have a problem with this,
though.

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The list of available x's from a location

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As you can see it's built up from
the keys of the exits dictionary.

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So we're using this to go through, we're
cycling through the line 42, the keys

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dictionary or the exits dictionary and
building up a list of available exits.

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So consequently of course when we run it,

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which you saw when I run it previously
We've got now all these numbers and

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they're 4, 3, 2,
5 as well as valid directions.

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Now that's actually a problem,
it doesn't look good.

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So what we really need to do is store the
nine destinations in a separate dictionary

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then combine then at the point
when we check the players input.

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And what we actually wanna do here,
I'll just connect that.

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Cuz you really wanna undo those
changes that we've made and

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create a combined directory.

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So am gonna undo this.

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The easiest way for me to fix this,
is to go back and just copy and

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paste from our old challenge.

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So am gonna copy the old exits And
I'll paste that in.

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Go back to our game.

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Pi file, paste that in.

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So we're left now with our original exits.

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So what we want to do is add
a new dictionary called name dex,

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that contains those numbers
that we've just removed.

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So, name x's equals 1.

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2 colon 2.

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3 colon three.

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Five: five and

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four colon four.

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So that's our first dictionary for
the location one.

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Location two, we only had the one,
and that was to location five.

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Location three, we only had one again.

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1, 4, we had a couple.

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We 1, 1 and also 2, 2.

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And lastly, location five Also had 2 so

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2:2 1:1 like so, so that's our NamedExits,

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so what we wanna do then is create a
combined directory Copy of the location's

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exit dictionary and updating it to
include the appropriate named exits.

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But there's no point doing all that
work if the player's charging to quit.

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So what we're going to do is add
an else clause to the check for

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location zero and
prepare our combined dictionary there.

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So down here if loc equals zero, break.

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And I'm going to add an else.

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If it's not location zero, which means
we're still moving to another room.

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And we're gonna type
allExits=exits(loc).copy,

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so I'm grabbing a copy
of that dictionary and

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allExits.update(namedExits[loc]), so

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we're grabbing a copy of all the exits

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That count in the exits
directory from here.

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And then what we're doing, and that's for
that particular location, and then so

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we've created a copy of that.

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It's on line 55.

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And then line 56 what we're
doing is we're updating it.

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So we're grabbing a copy of
the appropriate entries from the name

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dictionary for that location, and adding
to the new dictionary, which is all x's,

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which we've created.

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So consequently, now, instead of here on
line 68, checking for the x's location,

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at the x's current location,
we can change that and test for all x's.

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So we're just checking to see
whether our direction's in allExits.

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And of course, allExits contains both
the directions, north, south, east,

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west, but also the other locations,
the actual numbers, as well.

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And of course allExits again, we confirmed
now is the west, north, east, west, etc.

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But also the named exits
as in the numbers as well,

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allowing us to use that vocabulary for
that purpose.

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And the other thing to note is of course
we don't need to change anything here.

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So line 48, the available exits is
now going to correctly look at just

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the location, the exits for that
particular location, and it's not going to

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include any of those numbers that
we saw when we previously ran it.

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So now if we run this, You'll notice
now that the numbers have gone.

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We should be able to just
use our normal items.

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So what I'll do is we'll quit out of
that again and we'll run it again.

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Just to the same as what
we've been doing before.

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So south, north, road,
should be at the top road.

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Nothing will happen cuz we're already
there, but we can type, valley.

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And we got an error there.

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So it's probably a good time
to actually debug this.

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That's line 69 that's failing.

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And I suspect what I've done is I've coded
something incorrectly, one of the keys.

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And what I failed to do,
if we look at it, actually line 69,

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probably should have looked
at the error straightaway.

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If you look at that carefully,
lines 68 and 69,

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you can probably see what I've done.

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So we're looking in our
dictionary all exits

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then trying to retrieve
a location from the exits.

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So consequently, the code's gonna
work fine if we use west, north,

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east, south etc using
those sorta locations.

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But soon as we start typing in
the number it's gonna exit,

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it's going to crash rather
Because it doesn't exist.

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So what I should have done
there was make that all exits.

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And that should fix it, so we should
be able to run that again now, and

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still we have to go south, north, but
now we should be able to go valley,

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and go back to road.

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And if we just type road again we should
get an error because we can't go in

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that direction.

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So as you can see, update and copy,
really two very useful commands.

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So we've covered quite a lot of important
concepts in the discussion overall,

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of dictionaries.

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And it's gone over, now, quite a few
videos, including the way that we've

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related different data structures
by using the location,

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the loc variable to access entries in
both the locations and exits structures.

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And this is only one was to represent
allocations and keep that in mind.

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So our net could be modeled in very
different ways so keep that in mind and

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we could have used lists instead
of dictionaries for example.

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Now dictionaries have the advantage that
insertion and deletion are extremely fast.

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And that's of little relevance here,

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because we're not using those operations
but access by key is also extremely fast,

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which will be very useful for
a game like this.

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So I'm gonna finish the video here now.

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In the next video we're going
to go through another challenge.

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We're going to challenge around
a standing of dictionaries.

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So see you in the next video.