@property

Learn to define properties with @property.

The @property decorator

The @property decorator turns a method into something readable like an attribute. You access it without parentheses; this gives the outside a clean encapsulated look.

Example: class Account:\n @property\n def balance(self):\n return self._balance. Writing a.balance calls the method; not a.balance(). This makes it easy to update the inner logic later without changing how outside code accesses it; you can add computation, for instance.

Access without parentheses

A method marked with @property is called without parentheses. Writing a.balance is enough; a.balance() raises an error. This hides the difference between an attribute and a computed value from the outside.

So today it returns self._balance; tomorrow it can do a computation, while outside code stays unchanged. This is the core of encapsulation: stable outer interface, flexible inner data. Example: return self._balance * self._rate.

Exercise Add @property to Account

Define the Account class. Add def __init__(self, balance): with self._balance = balance in the body. Above add the @property decorator and a method def balance(self):; in its body write return self._balance. Then create an instance with a = Account(100) and call print(a.balance).

Show example solution

# Define the Account class with @property
class Account:
    def __init__(self, balance):
        self._balance = balance
    @property
    def balance(self):
        return self._balance

a = Account(100)
print(a.balance)

Test yourself

Complete the @property line

    ____
    def balance(self):
        return self._balance

Show answer

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

What does @property do?
- It deletes an attribute
- It creates a class variable
- It makes a method read like an attribute
- It makes a method static
Show answer

It makes a method read like an attribute — @property makes a method read like an attribute; no parentheses needed.
Match the @property concepts

@property

Getter decorator
a.balance

Parenthesis-free access
self._balance

Inner data

Next lesson: @x.setter

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