Creational Patterns

Factory

class Burger:
    def __init__(self, ingredients):
        self.ingredients = ingredients

    def print(self):
        print(self.ingredients)

class BurgerFactory:
    
    def createCheeseBurger(self):
        ingredients = ["bun", "cheese", "beef-patty"]
        return Burger(ingredients)
    
    def createDeluxeCheeseBurger(self):
        ingredients = ["bun", "tomatoe", "lettuce", "cheese", "beef-patty"]
        return Burger(ingredients)

    def createVeganBurger(self):
        ingredients = ["bun", "special-sauce", "veggie-patty"]
        return Burger(ingredients)

burgerFactory = BurgerFactory()
burgerFactory.createCheeseBurger().print()
burgerFactory.createDeluxeCheeseBurger().print()
burgerFactory.createVeganBurger().print()

Output

['bun', 'cheese', 'beef-patty']

 

['bun', 'tomatoe', 'lettuce', 'cheese', 'beef-patty']

 

['bun', 'special-sauce', 'veggie-patty']

Builder

class Burger:
    def __init__(self):
        self.buns = None
        self.patty = None
        self.cheese = None

    def setBuns(self, bunStyle):
        self.buns = bunStyle
    
    def setPatty(self, pattyStyle):
        self.patty = pattyStyle
    
    def setCheese(self, cheeseStyle):
        self.cheese = cheeseStyle

class BurgerBuilder:
    def __init__(self):
        self.burger = Burger()

    def addBuns(self, bunStyle):
        self.burger.setBuns(bunStyle)
        return self
    
    def addPatty(self, pattyStyle):
        self.burger.setPatty(pattyStyle)
        return self
    
    def addCheese(self, cheeseStyle):
        self.burger.setCheese(cheeseStyle)
        return self  

    def build(self):
        return self.burger

burger = BurgerBuilder() \
            .addBuns("sesame") \
            .addPatty("fish-patty") \
            .addCheese("swiss cheese") \
            .build()

Singleton

class ApplicationState:
    instance = None

    def __init__(self):
        self.isLoggedIn = False

    @staticmethod
    def getAppState():
        if not ApplicationState.instance:  
            ApplicationState.instance = ApplicationState()
        return ApplicationState.instance

appState1 = ApplicationState.getAppState()
print(appState1.isLoggedIn)

appState2 = ApplicationState.getAppState()
appState1.isLoggedIn = True

print(appState1.isLoggedIn)
print(appState2.isLoggedIn)

Output

False

 

True 

True