Python Jumpstart by Building 10 Apps Transcripts
Chapter: App 7: Wizard Battle App
Lecture: Concept: Polymorphism
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Let's look at the final core concept
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in this object oriented wizard game called polymorphism.
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Now you can see that we have a list of diverse creatures,
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we have small animals, creatures, dragons, wizards and so on,
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and as you saw on a previous examples
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and you can see in the note on the left here,
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all of these objects all of these classes, small animal, dragon and wizard,
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all derive from creature.
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Below we have a wizard named Gandolf.
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and if he is going to go on some kind of a rampage
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and just start attacking all the creatures
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he would say for c in creatures wizard.attack c,
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now when we write that attack method, we don't care or usually want to know,
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it's usually a negative thing to actually know whether it's a dragon
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a small animal or just a creature
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because we can leverage the fact that all of these derived from creature
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we can just work with the common functionality,
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the fields and the methods on the creature class and it doesn't matter
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what type of derived object we pass, it's a small animal, a dragon,
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we can still fight it just the same, we don't have to rewrite our code,
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and that's fantastic, that lets us as we evolve our application
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create more specialization other types of objects,
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later in the game we want to add some kind of like water monster
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to attack the wizard when he is out in the ocean or something
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as long as that thing derives from creature,
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we potentially don't have to rewrite the code
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that handles wizard's battling water monsters
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it's just using this base class.
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So that's a really powerful feature.
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One other concept closely related to this is something called duck typing,
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in statically typed compiled languages like C#, Java, C++ and so on,
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you absolutely must have these objects derived from creature
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or trying to pass them to the attack method
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which assumes it takes a creature or literally not compile, your code won't run ever.
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In Python it's not like that, Python uses something called duck typing
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and as long as the shape of the pieces of the creature class
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that the attack method assumes are there, get defensive roll, name,
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as long as the types you pass match that,
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you technically can use it here, and that is called duck typing,
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it's like if it acts like a creature, if it looks like a creature, it is a creature,
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but I still encourage you to create these object hierarchies
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as it helps reduce code duplication, it helps with maintenance
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and it's generally just the right thing to do.
