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Okay.
So it's time for a Python challenge.

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We're actually going to do
two challenges for these, for

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the dictionary sort of things.

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So the first one, let me introduce,
I'm gonna copy this code because

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ultimately we're going to be using
that and I'm gonna create a new file.

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A new Python File.

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And we'll call this challenge.

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I'm just gonna paste it in there.

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That's the standard code that we
worked on in the previous video.

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But what we're going to do,
come up to the top here.

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We're gonna paste in First challenge,
bearing in mind there's a couple of

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challenges here, and
we saw a couple of sections.

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So the challenge at the moment is to
modify the program that you see below, so

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that the exits are a dictionary
rather than a list.

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And the keys being the numbers of
the locations and the values being

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dictionaries holding the exits, and
obviously they're doing that at present.

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So no change should be needed
to the actual code itself,

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it's just basically the dictionaries and
lists that you're changing.

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And once that's working,

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we're gonna create another dictionary
that contains words That players can use.

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Instructions, in other words.

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And these words will be the keys, and

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the valleys will be a single letter that
the can use to determine which way to go.

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So that's the challenge.

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Two components of a challenge.

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And bearing in mind it's also a secondary
challenge which you will be doing later.

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So go away and
see if you can complete both of those and

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once you're ready come back and we'll work
through both parts of this challenge.

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Pause the video now.

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Okay, so how did you get on?

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Hopefully you managed to resolve that and
you've got it working.

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So the first stage is actually quite easy
so what we really want to do here is just

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change exits From a dictionary or sorry
from a list I should say to a dictionary.

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So let's go ahead now and make the change.

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Want to go ahead and

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convert the existing list which
is on line 18 into a dictionary.

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So to do that we're going to start by
removing the square brackets which

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indicate that it's a list.

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Like so and I'll just put a bit of
space here so it's a bit clearer.

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That we also need to put our keys in for
each part so zero colon,

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one colon,

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two colon.

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Three column, four column,
and five column.

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So the keys are obviously the rooms.

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The locations as they are before.

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And I'll just clear that
up a little bit like so.

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And that should be all we need to do.

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We've converted it now from
a list to a dictionary.

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If a key being the location 0, 1, 2, 3, 4,

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5 Which matches our location dictionary
above, so if we run that, and

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we should still be able to go
say north you're in the forest,

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south you're standing at the end of
a road we can quit, he's sitting

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in front of a computer learning Python so
that's the first part of the challenge.

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Converting it to a dictionary and

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note how we didn't have to change
any of the code that's the beauty

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that if we're using a numerical key for
a dictionary, the syntax for retrieving

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the dictionary value by key is the same
as retrieving a list item by index.

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That's one of the great things that
happened here, the code doesn't have to

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change to accommodate The change in the
data structure from list to dictionary.

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Okay so for the second part so

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we need to create a dictionary whose
keys are the words we're interested and

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the values of the single letter
that the program expects.

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So if the pro players talks
more than a single letter.

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Then we use the vocabulary dictionary.

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Because they could type
something like run less quickly,

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we don't use the text as the value to
look up, but we do it the other way.

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We iterate through the keys
to see if their text

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contains one of the words
that we recognize.

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So, what we need to do first is create our
vocabulary, we're going to put it down

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here and that's going to be a dictionary
with the relevant commands.

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So, we're going to start by
typing vocabulary equals and

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the first one will be quit and
the key, the value will be two.

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North, north, south,

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east, and west.

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[SOUND] And
we can just tidy it up a little bit so

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it sits there nicely, but that's optional.

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So we've now assigned the vocabulary.

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The dictionary.

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We've assigned and created a dictionary
and assigned it to vocabulary.

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The variable.

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So what we want to do
now is add some codes.

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So once we've actually got a command
that's been given to us and

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the users selected that and typed it in.

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Down here we want to
start adding some code.

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So we want to parse the input so
we're gonna parse user

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report using our vocabulary
dictionary if necessary.

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And we're only going to do that remember
if the length is greater than one.

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So I'm going to put if, len, direction,
direction, greater than one.

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In other words, more than one letter.

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Check out vocab.

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Then we put four word in vocabulary.

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So what effectively we're doing now
is does it contain a word we know?

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If word in direction,
if it does then direction,

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direction becomes equal
to vocabulary(word) and

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we'll just clean it up a little bit.

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And that's actually it
as you can see then.

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Remember, we're also converting
it to upper case as well.

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So we're really only testing
to see whatever they have

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typed is greater than 1, so
more than one character.

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If it is, we're gonna go through our
dictionary and try to find a match for

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whatever they have typed.

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And if they have typed
something like north,

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we're gonna match it back to
the value N as you can see there.

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Let's actually run this and
see if it works.

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So, first thing, you should just check.

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If you go north, you're in a forest.

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South, you're standing in the road.

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And if you type north, you're in a forest.

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But also you should be able to type,
go north.

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Your gonna first go south,
and the reason is

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we're actually done looking at our and
we're going through our dictionary and

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we're comparing each word of
the dictionary to see whether it's fine or

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whatevers being So, the entire string is
going south We are checking to see if

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the word South is actually in that string
and that's why it's working that way

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even though we've typed extra letters that
are not in it, exact match so to speak.

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So what we now got is
a fairly flexible way for

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players to specify which
direction they'd like to go in.

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And for that reason alone hopefully
that's demonstrated the power of using

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dictionaries.

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Once you are actually used to using
dictionaries Even our exits one.

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The exits diction where you will be
converted makes a lot more sense, but

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you can probably see why we chose
to use a list initially and

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that's because a dictionary
of dictionaries

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can look confusing at first until
you sort of understand the.

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Concepts.

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Now with that said, we can make
the program a bit more efficient though.

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So it's quite likely that our
vocabulary will grow quite large,

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whereas the text the players type
in will only be a few words.

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So as a result,

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it's really not efficient to perform
the word lookup the way we have.

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As we could literally end up iterating
through a large collection of keys before

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we find the one that's
in the player's input,

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that's contained in the player's input.

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A better way would be to check each
word that the player has typed to

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see if it's in the vocabulary.

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Cuz obviously, starting from that way,
rather than coming from the.

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Starting at the vocabulary and
going through that.

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Better to go the other way.

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And Python provides a way to do just that.

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So what we need to do is break up
the input that the [INAUDIBLE].

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Applies topped into individual words
in other words individual sequences of

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characters separated by spaces so really
what we want to do there is we want to do

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the opposite of join and in fact there is
a method to do that and its called split.

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And it does exactly what we want.

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So given a string,
the split command or the split

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method will split a string into a list
containing all the parts of the string

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that are separated by the delimiter of our
choice, which is gonna be a space here.

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And if we don't specify a delimiter,
it defaults to a space.

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But we could use commas,

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colons or any other type of text
that we want as a delimiter.

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So let's have a look at,
see that in action.

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What we want to do before we start,
we want to comment

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out the call of the [INAUDIBLE] So
I'm going to close this down.

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Disconnect.

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Let's go ahead and comment all that
code out for now, cuz we don't need it.

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Come back to that later.

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Comment all that out again with command
slash, which is control slash for

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Windows and Linux after selecting it, and
we'll put our code up here We're probably

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coming to that area as well, the lock = 1
because that's all part and parcel of it.

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So let's actually try the split function,
let's do a couple of examples.

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We can do a print locations 0.

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split, and also try print locations 3.

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split.

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Passing a parameter this time.

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I was, or, comma.

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And let's also try this one.

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Print.
Space.

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Dot.

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Join locations.

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Zero.

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Dot.

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Spirit.

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[SOUND] So, let's run this.

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So you can see what happened
with the first one.

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It splits, you are sitting in front of
a computer learning Python, into a list

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containing the 10 words, which is pretty
cool that it's done that automatically.

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The 2nd example gave a list, gives a list
containing 2 items, as you can see,

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because it's split based on the fact that
we passed the parameter of a comma, so

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it's using that a as a delimiter
instead of the default being a space.

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Which the split method will use
unless you give it a parameter.

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And incidentally if you didn't want
a leading space in the second list item,

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you could specify comma as a string to
split on if you wanted to do it that way.

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So split's the opposite of join so

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the final print is interesting if
as it turns out a little futile.

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So it uses split to split the text that
spaces, but then it also calls join

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on a string containing a single
space to join them back up again.

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So really the end result is the orignal
string that you worked with.

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Ok, so armed with this split method,

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we can rewrite the program to
work the correct way around.

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So I can check the players
input against the vocabulary,

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instead of the other way around.

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So let's go back and do that.

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And I'm going to comment these [INAUDIBLE]
out, like so, and I'm going to select

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the [INAUDIBLE] code that we Comment
it out, and do a command slash again.

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Just control slash on Windows and
Linux, and that makes it,

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more [INAUDIBLE] gets rid of the comments,
so that we can work on it again.

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So what we want to do here is see,

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in this method is this part here
after the [INAUDIBLE] direction.

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You really just want to
comment that out for now.

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[INAUDIBLE] I'll do is I'll delete that.

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So after the test to make sure that what's
been taught has more than one characters

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in it,
we do words equals direction of split.

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So we're splitting up the input using
the default delimiter of a space.

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Cuz we're gonna go through those words,
so for word in words.

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And we're going a test the other way
this time and we're putting if word In

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vocabulary direction
equals vocabulary word.

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And we can also break at that point.

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So you can see how we've
done it the other way now.

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So what we've done is we've taken doing
our searching based on what the users

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typed instead of going through the whole
dictionary, which Isn't a problem now, but

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if we started having hundreds of entries,
it could start slowing it down.

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So it's always something that you should
be looking at when you're developing code,

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to decide which angle should I start from.

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Is it best to start, in this case,
from the user's input,

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because chances are there's only
gonna be a few words there,

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instead of automatically processing
the entire dictionary each time,

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which we did in sort of
the first version of this code.

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Let's run this and make sure it works.

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So if we type east, okay, and

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now back to west again, and
if we type E, go back to west again.

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Please sir, can I go east.

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And it's gonna say it's found east,
so it's gonna [INAUDIBLE]

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each one of those words and found east
as the last word, And that works.

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So we go back west again.

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And just to make sure,

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how bout going east now again.

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And still found that as well.

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So that's it.
I hope

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you got a lot out of that challenge.

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So we're not done yet with dictionaries.

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In the next video, we're gonna go ahead
and continue our work on dictionaries.

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And specifically we're going to
be looking at the update method

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which allows you to
combine two dictionaries.

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And also a copy method that's used
to create a copy of a dictionary and

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then we'll go into another challenge for
that as well.

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So see you in the next video.