软件开发的坚实原则

class order:    def __init__(self, items):        self.items = items    def calculate_total(self):        return sum(item.price for item in self.items)class invoiceprinter:    @staticmethod    def print_invoice(order):        print("invoice:")        for item in order.items:            print(f"{item.name}: ${item.price}")        print(f"total: ${order.calculate_total()}")# usageclass item:    def __init__(self, name, price):        self.name = name        self.price = priceitems = [item("apple", 1), item("banana", 2)]order = order(items)invoiceprinter.print_invoice(order)

class discount:    def apply(self, total):        return totalclass percentagediscount(discount):    def __init__(self, percentage):        self.percentage = percentage    def apply(self, total):        return total - (total * self.percentage / 100)class fixeddiscount(discount):    def __init__(self, amount):        self.amount = amount    def apply(self, total):        return total - self.amountdef calculate_total(order, discount):    total = order.calculate_total()    return discount.apply(total)# usagediscount = percentagediscount(10)print(calculate_total(order, discount))

class bird:    def fly(self):        passclass sparrow(bird):    def fly(self):        print("sparrow is flying")class ostrich(bird):    def fly(self):        raise exception("ostrich can't fly")def make_bird_fly(bird):    bird.fly()# usagesparrow = sparrow()make_bird_fly(sparrow)ostrich = ostrich()try:    make_bird_fly(ostrich)except exception as e:    print(e)

from abc import abc, abstractmethodclass printer(abc):    @abstractmethod    def print_document(self, document):        passclass scanner(abc):    @abstractmethod    def scan_document(self, document):        passclass multifunctionprinter(printer, scanner):    def print_document(self, document):        print(f"printing: {document}")    def scan_document(self, document):        print(f"scanning: {document}")class simpleprinter(printer):    def print_document(self, document):        print(f"printing: {document}")# usagemfp = multifunctionprinter()mfp.print_document("report")mfp.scan_document("report")printer = simpleprinter()printer.print_document("report")

from abc import ABC, abstractmethodclass Database(ABC):    @abstractmethod    def save(self, data):        passclass MySQLDatabase(Database):    def save(self, data):        print("Saving data to MySQL database")class MongoDBDatabase(Database):    def save(self, data):        print("Saving data to MongoDB database")class UserService:    def __init__(self, database: Database):        self.database = database    def save_user(self, user_data):        self.database.save(user_data)# Usagemysql_db = MySQLDatabase()mongo_db = MongoDBDatabase()user_service = UserService(mysql_db)user_service.save_user({"name": "John Doe"})user_service = UserService(mongo_db)user_service.save_user({"name": "Jane Doe"})