Question 1

What is the relationship between __eq__ and __hash__ in Python?

Accepted Answer

If two objects are equal according to __eq__, they must have the same hash. Defining __eq__ alone makes Python set __hash__ to None, so the object becomes unhashable, and fields that feed the hash must not change while the object is a dict key or set element.

Question 2

What is the difference between a shallow copy and a deep copy?

Accepted Answer

A shallow copy creates a new container whose inner elements are the same objects, while a deep copy recursively copies the whole object graph, handling circular references.

Question 3

What is the difference between an iterable and an iterator?

Accepted Answer

An iterable is an object you can get an iterator from through iter() (such as a list); an iterator remembers its position, returns the next item through next(), and is consumed only once.

Question 4

How do generators and yield reduce memory usage?

Accepted Answer

A generator produces values on demand, one at a time, instead of building a full collection, so memory stays roughly constant no matter how large the data is.

Question 5

Which protocol makes an object usable in a for loop?

Accepted Answer

The object must define __iter__ returning an iterator, and the iterator defines __next__ that returns the next item and raises StopIteration at the end (and defines __iter__ returning self).

Question 6

When should you use a property instead of explicit getter and setter methods?

Accepted Answer

A property exposes a computed or validated value through plain attribute syntax, and you can start with a simple attribute and turn it into a property later without breaking the interface.

Question 7

What does the @dataclass decorator give you?

Accepted Answer

It automatically generates __init__, __repr__ and __eq__ (and optionally ordering, hash and freezing) from the fields declared with type annotations.

Question 8

What is __slots__ for, and what trade-offs come with it?

Accepted Answer

__slots__ declares a fixed list of attributes and removes the per-instance __dict__, which reduces memory and speeds up access slightly, but it prevents adding dynamic attributes and complicates inheritance.

Question 9

How do MRO and super() work with multiple inheritance?

Accepted Answer

The MRO (computed with the C3 algorithm) determines the order in which classes are searched for methods, and super() does not necessarily call the direct parent but the next class in the MRO of the actual object.

Question 10

Which protocol does a context manager implement?

Accepted Answer

The object defines __enter__ (for setup and returning the value bound by as) and __exit__ (for cleanup), or it is built easily with contextlib.contextmanager, and with guarantees the cleanup runs even if an exception occurs.

Data Model & Object Protocols Interview Questions (Python)

What is the relationship between eq and hash in Python?