Examples for the SOLID principles

solid_bad.py

"""Open/Closed Principle
Example inspired by this wonderful piece here: http://joelabrahamsson.com/a-simple-example-of-the-openclosed-principle/
"""

# Area calculator: calculate area of a rectangle
class Rectangle:
    def __init__(self, width, height):
        self.width = width
        self.height = height
    
    def area(self):
        return self.width * self.height

# Calculate area of multiple rectangles  
    
class AreaCalculator:
    

solid_good.py

"""
Single Responsibility Principle

Every module, class, or function should have responsibility over a single part 
of the functionality provided by the software.

User class handles one thing: the identity of a user. It's sole method does exactly 1 thing: changes the name property.
"""
class User:
    id = 1;
    name = '';

    def updateName(newName):
        this.name = newName
        console.log('Name updated.')


"""Open/Closed Principle
Example inspired by this wonderful piece here: http://joelabrahamsson.com/a-simple-example-of-the-openclosed-principle/
"""
class Shape:
    def area(self):
        NotImplementedError('You must implement this method!')
        

class Rectangle(Shape):
    def __init__(self, width, height):
        self.width = width
        self.height = height
    
    def area(self):
        return self.width * self.height

    
class Circle(Shape):
    def __init__(self, radius):
        self.radius = radius
    
    def area(self):
        import math
        return (self.radius**2)*math.pi
class AreaCalculator:
    def calculate(self, shapes):