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so it is nearly time for the challenge but
before we get into that what we want to do is go

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through and have a look at a common
source of errors when you're

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converting a dictionary that is
initialized using a literal into a shelve

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know this is one time unfortunately when
IntelliJ syntax checking doesn't help in

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detecting the error so it is worth being
aware of this so you know what to do in

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when this situation comes out so what we
gonna do is we're going to keep our

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recipes but we gonna make the dictionary a
little bit more complicated by adding to

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it

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a dictionary books so will use just two in this
case the recipes and the parts needed

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for performing maintenance on a motorcycle
now because this is a course on Python not motorcycle

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maintenance we are gonna keep it a bit
simple so a bit of the bike should move

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and if it doesn't will apply lubricant if it
does move and shouldn't will stick it

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down with gahfer tape so here is the dictionary we used to

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convert it into so I'll just type that up it is gonna be...

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....and its going to be....

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... and the last one for this book is pasta....

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and then we are going on to the
next book now and the next book is....

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we are going to call that maintenance.....

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and..so that is our definition as I said its a

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making a bit more complicated by adding
a dictionary books now so we got 2 book in

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there each with their own individual
parts in this case the first one was recipes

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the ingredients and the second one
was the things needed to fix a motor

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bike up or be it very simplistically and just to
confirm this works let's try doing a

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print....

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....print out the individual ingredients for soup...

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we should be able to do the same....

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...just to confirm that we can print out the ingredient lists....so lets just run that to confirm that it does work

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we got a typo there that should be recipes try again and you can see we got tin of soup which is the ingredient of soup we got eggs

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butter and milk which are ingredients for scrambled eggs and
gaffer tape which was correct for the

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loose key which is part of the
maintenance key pair so that's good so that is our key value

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so that is working fine now the conversion to shelve is
quite straightforward so after opening

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the shelve we just do a bit of editing to get it to
work so what we wanted to do is change the code

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and will do something like this, first is we import the shelve....

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and will put books..... and so
once we've done that all we can leave all

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the existing prints there because this
time it's now going to be printed to

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our shelve instead of printing out to the
screen so of course the last thing we need

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to do after all of that is do a books...and we just need to change it a little bit now

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because we've defined books above on line 4
what we need to do is we need to

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change this to put books.....and
down here what we need to do is we are getting

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down to this line and then we've got
books here....

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....and then of
course I have to fix this to get red of recipes and that should be fixed and of course right down at the end under books maintenance, of course there

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shouldn't be 2 braces it should be a single one
and Python being pedantic we need to to make sure that

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they line up correctly as well so want to remove any warnings
so once we've done that you can see now

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that we've got the green tick in the top
right hand corner of the screen so as

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far as IntelliJ is concerned everything is
good to go but when we try running it we get an error and you can

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see that the error that comes up is that
tuple indices must be integers

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or slices and not string or str now the
problem is caused over here on line 8 by

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leaving a

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comma at the end of that line now this
is a very easy mistake to make when

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converting a literal dictionary into
individual shelve assignments and what

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we've actually ended up is a
value to the key recipes that is a

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tuple

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consisting of a dictionary and an empty
entry and we can see that by changing

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line 12 if we just temporarily comment out these other ones out and we just
print out recipes instead of the ingredients

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for soup like that after removing the comma it
shouldn't have been there if we run it again

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now we can sort of see what the result is
we'll just scroll over you can see that the problem is fixed so

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it's really quite important when your converting a dictionary
into a shelve so keep that in mind we really

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need to take care to ensure that there's
no additional commas or curly brackets

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where you will get odd results and error that are
sometimes can be hard to debug so do

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keep that in mind when using shelve to
convert it as it was shown in this

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example ok so on with the challenge
so what I'm going to do now is create a new

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file so I'm gonna call this challenge and although we did say a shelve
perhaps not the best choice for

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persisting data in an adventure game we
have set up fairly complex dictionaries in

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this game

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and as is its structure that you'll
understand because we used it we're

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going to use that so you can focus on
the code changes rather than trying to

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understand yet another data structure so
this challenge will be good practice for

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switching dictionary to a shelve and also
vice versa should you need to but rest

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assured with that said that will not be using
shelves to persists the basic game data as

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we complete the game I'm gonna paste in
and let you know

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to show you what the challenges is ok so
here is the challenge and I've paste some code in

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from a previous challenge so what you
need to do is modify the program from

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the second dictionary challenge of
of lecture 56 and that's what these code

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is from to use shelves instead of the dictionaries
that we of course used in that challenge

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and you want to do this by creating two
programs first one should be called cave

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underscore initialize dot py and that
should create the two shelves which are

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locations and vocabulary with the
appropriate keys and values and second

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file that you want to create is called cave underscore
game dot py and that

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will then used the two shelves instead of
using dictionaries so apart from opening

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and closing the shelves

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cave_game would need only to change to
the actual code remember that shelve keys

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must be strings so that's very important to
keep in mind and just to be clear the

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cave_game py will contain the code
from line 45 on words below so in other

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words the code starting with this loc = 1 through to the end everything before

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that as you can see here on lines 14 through 43
are inclusive that ultimately gonna be modified

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to use shelve being cave_initialize.py so

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essentially the process will be that you will run
cave_initialized.py and that will

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create the necessary shelves then of
course in the cave_game.py that

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is gonna be using those shelves and
that where you actually run the

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game itself so that's the challenge now is
the time to pause the video and go away

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and see if you can figure out that challenge
and when you done come back and you can

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compare what you come up with our solution
so we'll see when you get back

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ok so how did you get on, hopefully you got it to work so what we going to do is start
on cave_initialize.py so I want to take

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a copy of that and I'm going to create
the new Python file and call that cave_initialized.py

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and that's going to be our initialization
code obviously we got the code here that

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we're going to be reliant on and that does need
to be changed so we're going to do is

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I'm going to just take that code so you
can see what I'm doing to change it

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the code up to an including line 43 I'm gonna paste that in

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two our cave_initialize.py then I'm going to go back up
to line 1 and start making some

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changes so first I'm gonna import shelve....obviously need that
so you can write shelves out and will start with location so

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locations....that is ultimately going to be the name of our shelve so what we wanna do now is convert these remembering that we

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need to use strings as keys for a shelve and
obviously as you can see right now this

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is not the case we're not
using strings there we are using entered

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integers so a way to changes could
be to changes this code a little bit so we could

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put locations...put the location in as a string as you can see there and

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set that to equals

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so get rid of that first part, and the exits is good and the name exits
is fine but we will then get rid of the

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the comma in the end of the line we are gonna do that for each line
so I'm gonna copy some of this code so just to be a bit quicker go

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back to the start of the line paste that in, this is location 1...and the next one

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location 2...and I'm deleting the commas as you can see each time, remember we talked about

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that earlier in the video how that's
important location 3....and 4....and the last one obviously

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5... and we get rid of that brace which we no longer
need and we can probably fix these up just to

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indent them so that Python is happy with
the indentation and I'm getting a warning there ok so that fixed all those up so

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that is the first part and we need to do the
similar thing now for second part

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obviously the second part vocabulary
is using a key currently a string and not

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as an integer but we still need to
convert it into that format so doing

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something like...and that's the code I'm going to copy actually I won't do that because it is a typo

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vocabulary...will copy that part as we did before and I'm going to

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come over here and copy that part quit....and of course what I need to do their is start making the shelves so...and now we can continue on with our

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copy and paste....

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..and next one is east...and next one is west....and road...hill...

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..valley...and last one is forest....and last thing to do here in order is we put vocabulary.close and the location.close and probably we could do there is we could close on this line because there is no reason to have it close rather than

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having to shelves opening at once not that it really matters

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but it is good practice to have all the
code in some areas so we are opening the shelve here

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we're performing the operation when want then we
close it immediately and likewise with vocabulary

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add some spaces so its a bit more readable

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that's should be the it that is the initialization set
up and we will add a new line there to keep you it happy

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and we should have a green tick in the top
right hand corner which we've got so that's good

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so just a recap what we had to do was because
shelve keys have to be strings which we

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talked about we had to change all the numeric
entries representing the locations

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firstly two strings and you can see they are all done now on lines 5 to 25 and then

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we did a similar thing for the vocabulary
even though they were already strings

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and not integers we still just change the
format to make it a bit easier and a bit

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more consistent so at this point we're
actually done so we've got the

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initialization down cave_initialized.py in the next video

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will come back and we'll make the
changes to cav_game so that

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we can get that working so see you in the
next video