What do __getitem__ and __iter__ enable on a custom class?
PICTURE THIS: DATABASE INDEX
Simple meaning
__getitem__ implements indexing and slicing, and if it raises IndexError, for-loops can treat the object as a sequence.
WHY — Dunder Methods instead of guessing?
Why interviewers care about Dunder Methods:
people who only read docs from people who shipped.
and tied to Python work.
Name the idea, why it exists, then one short example.
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__getitem__ implements indexing and
slicing, and if it raises IndexError, for-loops can treat the object as a sequence.
- 2__iter__ returns an iterator
and is the preferred way to make an object iterable.
- 3Implementing both consistently keeps
Django-style APIs unsurprising.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
__getitem__ implements indexing and slicing, and if it raises IndexError, for-loops can treat the object as a sequence. __iter__ returns an iterator and is the preferred way to make an object iterable.