Moderate OOP Question 91 of 228

When should you prefer composition over inheritance?

Python & Django · Speak this in 60–90 seconds · Faridabad & Delhi NCR

PICTURE THIS: DJANGO MVT

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ViewBusiness logic

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Simple meaning

Use inheritance for true is-a relationships and shared polymorphic APIs.

WHY — OOP instead of guessing?

Why interviewers care about OOP:

They are checking judgment

on OOP.

A good answer names

the situation, the default choice, and one exception - that reads as experience.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

STEPS — What happens step by step?

Before you speak the answer, walk the interviewer through these steps:

1
Use inheritance for true
is-a relationships and shared polymorphic APIs.
2
Use composition when you
want to reuse behavior by holding another object, which avoids brittle parent coupling.
3
Django favors mixins for
CBVs, which is a controlled form of multiple inheritance, not deep class trees.
4
Give an example
One tiny concrete case you can say aloud.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

EXAMPLE — See it in action

Here's a short line you can speak, broken into clear beats:

Say this line

“Use composition when you want to reuse behavior by holding another object, which”

Break into beats

Usecompositionwhenyouwantto

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Key takeaway

Use inheritance for true is-a relationships and shared polymorphic APIs. Use composition when you want to reuse behavior by holding another object, which avoids brittle parent coupling.