3. Operations declaration and inheritance

• Add the method statement to the Account class that prints a list of deposit and withdrawal operations.

• Change the __init__ method to use the deposit method to initialize the balance.

3.1. Client Class and Improved Account Class

class Client: def __init__(self, name, phone): self.name = name self.phone = phone class Account: def __init__(self, clients, number, balance=0): self.balance = 0 self.clients = clients self.number = number self.operations = [] self.deposit(balance) def summary(self): print("Account number: %s \nBalance: %10.2f" % (self.number, self.balance)) def withdraw(self, amount): if self.balance >= amount: self.balance -= amount self.operations.append(["Withdrawal", amount]) else: print("Not enough funds for withdrawal") def deposit(self, amount): self.balance += amount self.operations.append(["Deposit", amount]) def statement(self): print("Account Statement %s" % self.number) for op in self.operations: print("%10s %10.2f" % (op[0], op[1])) print("%10s %10.2f\n" % ("Balance", self.balance))

3.1.1. Using the Client and Improved Account Classes

juan = Client("Juan de Silva", "777-1234") maria = Client("Maria de Silva", "555-4321") account_1 = Account([juan], 1, 1000) account_2 = Account([maria, juan], 2, 500) account_1.withdraw(50) account_2.deposit(300) account_1.withdraw(190) account_2.deposit(95.15) account_2.withdraw(250) account_1.statement() account_2.statement()

3.2. Inheritance

• Object inheritance allows us to modify our classes by adding or modifying attributes and methods based on the previous class.

• We will create special accounts where we can withdraw more money than the balance, up to a certain limit.

• Deposit, withdrawal, and summary operations continue as a regular account.

3.3. Special Account Class

class SpecialAccount(Account): def __init__(self, clients, number, balance=0, limit=0): Account.__init__(self, clients, number, balance) self.limit = limit def withdraw(self, amount): if self.balance + self.limit >= amount: self.balance -= amount self.operations.append(["Withdrawal", amount]) else: print("Not enough funds for withdrawal")

• Note that we wrote Account in parentheses.

• SpecialAccount inherits the methods and attributes of Account.

• self.limit will only be created for classes of type SpecialAccount.

• Note that we are completely overriding the withdraw method in SpecialAccount.

3.4. Advantages of Inheritance

• We have made minimal changes to our program, maintaining previous functionality and adding new features.

• It was possible to reuse account methods.

• Therefore, the definition of the SpecialAccount class was much simpler, including only the different behavior.

3.5. Using all classes

juan = Client("Juan de Silva", "777-1234") maria = Client("Maria de Silva", "555-4321") account_1 = Account([juan], 1, 1000) account_2 = SpecialAccount([maria, juan], 2, 500, 1000) account_1.withdraw(50) account_2.deposit(300) account_1.withdraw(190) account_2.deposit(95.15) account_2.withdraw(1500) account_1.statement() account_2.statement()

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