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ok so as well as adding extra behavior

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to our subclasses we can also change

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the behavior of methods that exists in

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the superclass so to see how to do that

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we need to create a new vampire enemy

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but i think that makes for a good

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challenge

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ok so the challenge for you is to create

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that new vampire class that's a subclass

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of enemy now vampires have three lives

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and take 12 hit points of damage you can

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create a new python file for the

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vampire if you like but I've actually

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suggest adding it to the existing enemy

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.py file

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you want to test your class by creating

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one or two vampire instances and

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displaying their details also inflict

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some damage to make sure that the

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take_damaged method is working ok

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and also make sure that the trolls can

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also take damage because we haven't

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tested that so far

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alright so that's a challenge see how

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you go with it pause the video and I'll

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see you when you get back

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ok so let's go through my solution so

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what I'm going to do is add the vampire

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class to the enemy.py

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so....

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...

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...

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now we're going to be coming back

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to add more features to our class that

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vampire class but for now that's all we

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need for the challenge

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let's test this I'm going to go

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back to the main .py file the

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first thing we need to do is import the

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vampire class into this file so I'm

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going to add a comma at the end...

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again the warning because it's

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unused at the moment unused import

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statement going to delete the monster

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references out but let's actually add a

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vampire....

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...

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...

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....so that's

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clearly working ok ok now because our

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trolls and vampires all inherit from

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enemy they have all the methods that the

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enemy class defines so we can inflict

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damage on both trolls and vampires by

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calling the take_damaged method so

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let's go add some damage to the

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second troll...

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...

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...

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...so let's just confirm this

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will run it scrolling up we can see I

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took 18 points of damage have five left

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the message that was for ugh and ugh

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has now no more live one-hit points5 and

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scrolling down that took 5 points

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damages got seven left and you can see

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the confirmation of that live 3.7 but we

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should really test the other path

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through the take damage

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let's give ugh a hefty thrak with the

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sword glandarin and inflict 30

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points of damage and go back and do that

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will separate this will do...

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...

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...

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...i'm going to

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switch this to floating mode so that it

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doesn't affect the subtitles at the

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bottom of the screen then click on that

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that's going to put the run window up a

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little bit higher still be down a little

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bit more as well but you can also

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hide it when running it actually

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going to close it for now and run again we

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can see that ugh is now live 0 hit points5 so

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I'm still got a problem with hit points

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but you can see that ugh has lost a life

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here and we haven't got the message that

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appears when he's got zero or more hit

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points left so clearly this is something

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we need to fix close that down for now

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and go back to enemy.py

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really when a monsters got no lives

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left there dead at the moment you saw

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that we can keep fighting ugh

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had written a attack method it fought back

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that's not good but what is good is that

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we don't have to make changes to all

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our monsters

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okay we only got 2 at the moment but you

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could create 8 or 90 monsters in

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the game

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adding code to each class to track when the

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monsters dead would be a lot of work

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with that many enemies we also have to

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test the code for each monster to make

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sure we hadn't introduced to bug but

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getting back to our enemy class because

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all our monsters all subclasses the

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enemy class we can just add the

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necessary code to the enemy superclass

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and will be then automatically available

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in all subclasses so let's go ahead and

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make a change to start tracking when

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they reach their hit points where there

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should be dead and to do that want to

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start on here on line 8 by adding

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another attribute is going to be...

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....and what we

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want to do is have a look at this code

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in the take damage method and it's under

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this else where the life's self.lives

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is minus equal to 1 we need a

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test their the test is going to be...

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....

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....

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ok confirming that we've got a new

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attribute called alive that's

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initialized to true init method on line 8

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we then change the take_

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damage method so after losing a

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life we check to see if the life's left

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is still greater than 0 if the monster

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still has lives left

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we print a message saying they lost a

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life you can see that here on line 18

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and otherwise we set self.alive to

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false line 21

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that's because they're no longer alive

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because they reached 0 lives left

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let's confirm that this works

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so we're going to come down here and add

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some code let's add some code via a

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while loop that tests while the vampire is

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alive so...

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...

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...

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...basically going to keep

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taking one point of damage until all his

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life is overt in which case at that

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point the alive attribute will change

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from true to false the whille will exit

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and then the program should exit as well

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let's just run this to see if it works

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you can see there that we've got

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vlad take some damage there we got down

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to zero points left lost a life

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notice also hear he's lost another life

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and another life because hit points

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didn't get reset that's something we'll

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need to look at to reset the hit points

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back to a value when he has lost a life

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but he's still alive but you can see the

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principle of continuing taking damage

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until he has died works the loop exit

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and once you got to 0 lives blood was

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dead

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and the program exited and also up here

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ugh was dead as well at that point and

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again you could argue that we should be

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putting the hit points back to their

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original values when the monster

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losses a life

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that's up to as the designer of the class

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and if makes more sense for the

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monsters to behave like that then of

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course you're the Creator you can do

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that

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alright so i'm going to stop the video

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here now we've seen how to give a

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subclass additional behavior when we

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added the grunt method to the troll

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class in the next video we're going to

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look at how to override methods of the

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superclass to change the way that a

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subclass behaves and what I'll do is I'll

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just run it one more time I'm just gonna

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take this out of floating mode putting

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that back their on the screen

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okay i'll see you in the next video