Python for Entrepreneurs Transcripts
Chapter: Appendix: Python language concepts
Lecture: Concept: Inheritance

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0:01 A key design feature for working with classes and object-oriented programming
0:04 is modeling and layers, going from the most general to the most specific.
0:09 So, we started with a creature class,
0:12 and a creature class has a name and a level and it's just a generic creature,
0:16 it could be anything, so it could be a squirrel as we saw,
0:20 it could be a dragon, it could be a toad.
0:23 Any kind of creature we can think of, we could model with the original creature class,
0:26 and that's great because it's very applicable but there are differences
0:30 between a dragon and a toad, for example,
0:33 maybe the dragon breathes fire, not too many toads breed fire,
0:36 and so we can use inheritance to add additional specializations to our more specific types,
0:43 so we can have a specific dragon class, which can stand in for a creature,
0:47 it is a creature but it also has more behaviors and more variables.
0:51 Here we have our initializer, the __init__
0:54 and you see we take the required parameters
0:57 and data to pass along to the creature class,
1:00 in order to create a creature, in order for the dragon to be a creature,
1:03 it has to supply a name and a level,
1:05 so we can get to the creature's initializer saying super().__init__
1:09 and pass name and level and that allows the creature to do
1:12 whatever sort of setup it does when it gets created,
1:14 but we also want to have a scale thickness for our dragon,
1:17 so we create another field specific only to dragons,
1:20 and we say self.scale_thickness = whatever they passed in.
1:23 So in addition to having name and level we get from Creature,
1:26 we also have a scale thickness,
1:28 so that adds more data we can also add additional behaviors,
1:30 here we have added a breed_fire method.
1:33 So the way we create a derived type in Python,
1:36 is we just say class, because it is a class, the name of the class, Dragon,
1:40 and in parenthesis the name of the base type.
1:44 And then, other than that, and using "super",
1:46 this is basically the same as creating any other class.