Property decorator usage in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of property getter

What is the output of this code?

Python

class Circle:
    def __init__(self, radius):
        self._radius = radius
    
    @property
    def radius(self):
        return self._radius

c = Circle(5)
print(c.radius)

A AttributeError

B 5

C None

D TypeError

💡 Hint

Look at how the property decorator allows access to the private variable.

The @property decorator makes the method 'radius' behave like an attribute. So, c.radius returns the value of self._radius, which is 5.

❓ Predict Output

intermediate

Output after setting property value

What will be the output of this code?

Python

class Person:
    def __init__(self, name):
        self._name = name
    
    @property
    def name(self):
        return self._name
    
    @name.setter
    def name(self, value):
        self._name = value

p = Person('Alice')
p.name = 'Bob'
print(p.name)

A Alice

B AttributeError

C Bob

D None

💡 Hint

The setter changes the private variable _name.

The setter method allows changing the value of _name through the property 'name'. So after setting p.name = 'Bob', printing p.name outputs 'Bob'.

❓ Predict Output

advanced

Output with property and deleter

What is the output of this code?

Python

class Data:
    def __init__(self):
        self._value = 10
    
    @property
    def value(self):
        return self._value
    
    @value.deleter
    def value(self):
        del self._value

d = Data()
print(d.value)
del d.value
print(hasattr(d, '_value'))

A

TypeError
True

B

10
True

C

AttributeError
False

D

10
False

💡 Hint

Deleting the property deletes the underlying attribute.

The deleter removes the attribute _value. After deletion, hasattr(d, '_value') returns False. The first print shows 10 before deletion.

❓ Predict Output

advanced

Error when setting read-only property

What error does this code raise?

Python

class ReadOnly:
    @property
    def data(self):
        return 42

r = ReadOnly()
r.data = 10

A AttributeError

B TypeError

C SyntaxError

D ValueError

💡 Hint

Properties without a setter are read-only.

Since 'data' has no setter, trying to assign to it raises AttributeError.

🧠 Conceptual

expert

Why use property decorators?

Which of the following is the main advantage of using property decorators in Python classes?

A They allow methods to be accessed like attributes, enabling controlled access to private variables.

B They automatically make all class variables public.

C They replace the need for constructors in classes.

D They speed up the execution of class methods significantly.

💡 Hint

Think about how properties help with encapsulation and attribute access.

Property decorators let you define methods that act like attributes, so you can control getting, setting, and deleting private variables while keeping a simple interface.