Python's Instance, Class, and Static Methods Demystified

methodTypes.py

import math

class MyClass:
    def method(self):
        return 'instance method called', self

    @classmethod
    def classmethod(cls):
        return 'class method called',cls

    @staticmethod
    def staticmethod():
        return 'static method called'

obj = MyClass()
print(obj.method())
print(obj.classmethod())
print(obj.staticmethod())

print(MyClass.classmethod())
print(MyClass.staticmethod())
# print(MyClass.method())
#TypeError: method() missing 1 required positional argument: 'self'

class Pizza:
    def __init__(self, ingredients, radius):
        self.ingredients = ingredients
        self.radius = radius

    def __repr__(self):
        return (f'Pizza({repr(self.radius)}, ' 
                f'{repr(self.ingredients)})')
    #@property
    def area(self):
        return self.circle_area(self.radius)

    @staticmethod
    def circle_area(r):
        return r ** 2 * math.pi

    @classmethod
    def margherita(cls):
        return cls(['mozzarella','tomatoes'] ,2)

    @classmethod
    def prosciutto(cls):
        return cls(['mozarella','tomatoes','ham'], 4)

obj = Pizza(['cheese', 'tomatoes'], 5)
print(obj) # Pizza(['cheese', 'tomatoes'])
print(Pizza.margherita() , Pizza.prosciutto())

p = Pizza(['mozzarella', 'tomatoes'] ,4)
print(p.area())
print(Pizza.circle_area(4))

'''One way to look at this use of class methods is that 
they allow you to define alternative constructors for your classes.

They all use the same __init__ constructor internally and simply 
provide a shortcut for remembering all of the various ingredients.'''