Basics - Classes

Python classes basics

The stuff below is like Python classes 101. It’s mostly either directly copied from or else loosely inspired by the Python manual

# define a new class
class MyClass:
    x = 123

    def greet(self):
        return "Hello from MyClass"


x = MyClass()

# see class attributes
x.greet()
x.x

123

Init Method

# we can define an __init()__ method to help us create object instances with specific initial states
class MyClass:
    def __init__(self, x):
        self.x = x

    def greet(self):
        return "Hello from MyClass"


y = MyClass(x=1)
y.x

1

Class Variables and Instance Variables

# class variables will be shared by all instances, whereas instance variables will be unique to each instance
class Dog:
    kind = "canine"  # class variable

    def __init__(self, name):
        self.name = name


d = Dog("Nala")
e = Dog("Adi")

d.name
d.kind
e.name


# below might be a way to create a Dog class where each dog has its own set of tricks
class Dog:
    kind = "canine"

    def __init__(self, name):
        self.name = name
        self.tricks = []

    def add_trick(self, trick):
        self.tricks.append(trick)


d = Dog("Nala")
d.add_trick("roll over")
d.add_trick("sit")

d.tricks

['roll over', 'sit']

Class Inheritance

Class inheritance lets classes inherit variables and methods from other classes

# classes also support inheritance
class Animal:
    def __init__(self, name):
        self.name = name


class Cat(Animal):
    kind = "cat"


a = Cat("Fluffy")

a.name
a.kind

'cat'