Classes

Classes are higher order data structures in which we can define our own methods and variables on. Think about this as creating your own datatypes that do not come with base Python.

Lets look at a basic class example:

# We use the "class" statement to create a class
class Human:

    # A class attribute. It is shared by all instances of this class
    species = "H. sapiens"

    # Basic initializer, this is called when this class is instantiated.
    # Note that the double leading and trailing underscores denote objects
    # or attributes that are used by Python but that live in user-controlled
    # namespaces. Methods(or objects or attributes) like: __init__, __str__,
    # __repr__ etc. are called special methods (or sometimes called dunder
    # methods). You should not invent such names on your own.
    def __init__(self, name):
        # Assign the argument to the instance's name attribute
        self.name = name

        # Initialize property
        self._age = 0   # the leading underscore indicates the "age" property is
                        # intended to be used internally
                        # do not rely on this to be enforced: it's a hint to other devs

    # An instance method. All methods take "self" as the first argument
    def say(self, msg):
        print("{name}: {message}".format(name=self.name, message=msg))

    # Another instance method
    def sing(self):
        return "yo... yo... microphone check... one two... one two..."


bob = Human("Bob") # we can create classes by calling them like functions
                   # on initialization, classes call their __init__ method 
                   # as a template for how to "build" the class

bob.say("hi!")     # just like we've done on other classes, we can call methods
bob.sing()         # these are called instance methods, since they run on 
                   # the instance of the class

In the next couple of sub lessons we will look at each of these parts in more depth.

Contributors: