Python Jumpstart by Building 10 Apps Transcripts
Chapter: App 7: Wizard Battle App
Lecture: Concept: Objects vs. Classes
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Let's take a moment and focus on this concept of classes versus objects.
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If you are new to object oriented programming and this idea of classes,
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this can be a little bit tricky.
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Recall, this is how we define a class,
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we say class creature and it defines basically the blueprint.
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Here is how we initialize it, and within that initialization here is the fields,
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here is the other behaviors it has for example that it can walk around
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and for creatures, there is only one creature class,
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this is it, this is what a creature looks like in our program.
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However, we can create many of these creatures,
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here we are going to create a squirrel and its power,
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you can see the parameter to the initialization method is power
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so here we want to say creature (7),
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we'recreating a squirrel with power 7 whatever that means
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and then we are also creating a dragon which is more powerful, it has power 50,
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so when we create the squirrel and the dragon,
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these are objects, and objects are created via classes
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but they each have their own pointer in memory
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and that points to their own data.
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So, this squirrel object it has its own power variable and its power is 7.
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Now it actually gets the implementation from walk, from the blueprint,
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but we can call walk on this squirrel and we'll work with its data,
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its power of 7 and so on.
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The dragon has another pointer,
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somewhere else in the memory and it has its own copy of power,
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so if we change the dragon's power
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obviously it's unrelated to the creature so these are objects,
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they are created from the class, from the blueprint of what defines a creature,
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and then we can call squirrel.walk(), dragon.walk()
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and they may have different behavior based on the power,
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maybe if there is a lot of power it jumps around
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if it doesn't have much it sort of scurries or something like this.
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Once you get used to this idea of classes and objects
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it's really straightforward and you'll have it down no problem,
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but if this is new to you, make sure that you get this idea,
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it's the core concept in object oriented programming
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classes, inheritance in object oriented programming
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play a really central role in Python.
