Private attributes in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of accessing a private attribute directly?

Consider this Python class with a private attribute. What happens when we try to print it directly?

Python

class MyClass:
    def __init__(self):
        self.__secret = 'hidden'

obj = MyClass()
print(obj.__secret)

A hidden

B None

C AttributeError

D SyntaxError

💡 Hint

Private attributes are not accessible directly outside the class.

In Python, attributes with double underscores are name-mangled and cannot be accessed directly outside the class, causing an AttributeError.

❓ Predict Output

intermediate

How to access a private attribute using name mangling?

Given a class with a private attribute, what is the output when accessing it using name mangling?

Python

class MyClass:
    def __init__(self):
        self.__secret = 'hidden'

obj = MyClass()
print(obj._MyClass__secret)

A hidden

B AttributeError

C None

D SyntaxError

💡 Hint

Private attributes are stored with a name that includes the class name.

Python changes the name of private attributes by prefixing them with _ClassName, so accessing obj._MyClass__secret works.

❓ Predict Output

advanced

What is the output when modifying a private attribute inside a subclass?

Look at this code where a subclass tries to modify a private attribute of its parent. What is printed?

Python

class Parent:
    def __init__(self):
        self.__value = 10

class Child(Parent):
    def __init__(self):
        super().__init__()
        self.__value = 20

obj = Child()
print(obj._Parent__value)

A None

B 20

C AttributeError

D 10

💡 Hint

Private attributes are name-mangled per class, so subclass private attributes are different.

The Child class creates its own private attribute _Child__value, so _Parent__value remains 10.

❓ Predict Output

advanced

What error occurs when trying to access a private attribute with a single underscore?

What happens when you try to access an attribute with a single underscore prefix from outside the class?

Python

class MyClass:
    def __init__(self):
        self._hidden = 'secret'

obj = MyClass()
print(obj._hidden)

A secret

B AttributeError

C SyntaxError

D None

💡 Hint

Single underscore means 'protected' by convention, but no real restriction.

Attributes with a single underscore are accessible outside the class; it's just a convention to treat them as non-public.

🧠 Conceptual

expert

Why does Python use name mangling for private attributes?

Choose the best explanation for why Python uses name mangling (double underscore prefix) for private attributes.

A To make attributes completely inaccessible from outside the class, enforcing strict privacy.

B To prevent accidental access and name clashes in subclasses by changing the attribute name internally.

C To optimize memory usage by shortening attribute names at runtime.

D To allow attributes to be accessed only by functions defined in the same module.

💡 Hint

Think about how subclasses might accidentally overwrite attributes.

Python's name mangling changes attribute names to include the class name, avoiding accidental overwrites in subclasses but does not enforce strict privacy.