Move from Excel to Python with Pandas Transcripts
Chapter: Appendix: Python language concepts
Lecture: Concept: Classes

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0:01 Classes and object-oriented programming are very important parts
0:04 of modern programming languages and in Python, they play a key role.
0:08 Here we are creating a class that we can use in some kind of game
0:12 or something that works with creatures.
0:15 So to create a creature class, you start with the keyword class,
0:18 and then you name the type and you say colon
0:21 and everything indented into that block
0:23 or that code suite to do with the class is a member of the class.
0:27 Most classes need some kind of initialization to get them started,
0:30 that's why you create a class, we want them to start up all ready to go
0:34 and bundled up with their data and then combine that with their methods,
0:38 their behaviors and they make powerful building blocks in programming.
0:42 So most classes will have an initializer,
0:45 and the initializer is where you create the variables and validate
0:48 that the class is getting setup in correct way, for example making sure the name is not empty,
0:52 the level is greater than zero, but less than a 100, something like that.
0:56 Now this is often refered to as __init__ sometimes just init,
1:01 or even a constructor and these dunder methods
1:04 because they have double underscores at the beginning and at the end,
1:07 they are part of the Python data model which lets us control many things about classes,
1:10 so you'll see a lot of methods like this but the __init__ method
1:13 is probably the most common on classes.
1:16 If you want to create behaviors with your class,
1:19 and if you have a class that's almost certainly part of what you are going to do,
1:22 you are going to define methods just like functions that are standalone,
1:26 methods or functions that are parts of classes
1:29 and you define them in exactly the same way,
1:32 the only difference is typically they take a self parameter,
1:35 the self parameter is passed explicitly everywhere when you are defining the class,
1:40 some languages have a "this" pointer, that's sort of implicit but in Python,
1:45 we call this self and it refers to the particular instance of the creature that exists,
1:50 you might have many creatures but the self is the one that you are working with currently.
1:54 So just be aware you have to pass that explicitly everywhere
1:58 unless you have what is called a class method or a static method.