Property decorator usage in Python - Mini Project: Build & Apply

Using the Property Decorator in Python

📖 Scenario: You are creating a simple program to manage a bank account. You want to control how the account balance is accessed and updated safely.

🎯 Goal: Build a Python class called BankAccount that uses the @property decorator to get and set the account balance with validation.

📋 What You'll Learn

Create a class named BankAccount with a private attribute _balance.

Add a @property method called balance to get the current balance.

Add a setter for balance that only allows setting a non-negative value.

Print the balance after setting it.

💡 Why This Matters

🌍 Real World

Property decorators help control access to important data in programs, like bank balances, ensuring data stays valid.

💼 Career

Understanding property decorators is useful for writing clean, safe code in many Python jobs, especially in finance, data management, and software development.

1

Create the BankAccount class with a private balance

Create a class called BankAccount with an __init__ method that sets a private attribute _balance to 0.

Python

class BankAccount:
    def __init__(self):
        # Your code here

Need a hint?

Use self._balance = 0 inside the __init__ method to create a private balance.

2

Add a property to get the balance

Add a @property method called balance inside the BankAccount class that returns self._balance.

Python

class BankAccount:
    def __init__(self):
        self._balance = 0

    # Your code here

Need a hint?

Use @property above the balance method to make it a getter.

3

Add a setter to update the balance safely

Add a setter for balance using @balance.setter that sets self._balance only if the new value is not negative. If the value is negative, do not change self._balance.

Python

class BankAccount:
    def __init__(self):
        self._balance = 0

    @property
    def balance(self):
        return self._balance

    # Your code here

Need a hint?

Use @balance.setter to create the setter method. Check if value is not negative before setting.

4

Create an account, set balance, and print it

Create an instance of BankAccount called account. Set account.balance to 100. Then print account.balance.

Python

class BankAccount:
    def __init__(self):
        self._balance = 0

    @property
    def balance(self):
        return self._balance

    @balance.setter
    def balance(self, value):
        if value >= 0:
            self._balance = value

# Your code here

Need a hint?

Create the object, set the balance to 100, then print the balance to see the result.