What are Python's built-in data types? | Interview Question

Q: What are Python's built-in data types?

**Target Audience:** Beginners preparing for Python interviews — no prior Python knowledge assumed. **Difficulty:** Easy **Python version:** Behaviour checked on CPython 3.11 (python3.11 and the in-page Pyodide 0.25.1 runtime, which is CPython 3.11.3). > **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. Every output shown in the **Verified** section was copied from a real run of the examples on this page. ## 1. Why This Even Matters — A Story First Think of a well-organised kitchen. Flour goes in a jar, eggs in a carton, spices in a rack of small labelled tins, and leftovers in a box with a lid you can open and refill. Each container is good at one job: the egg carton keeps things in a fixed order, the spice rack lets you find "cumin" by its label, and the leftovers box can be emptied and refilled. Try storing soup in the egg carton and you get a mess. Python's bui

The problem

Question presented to candidate: "Python is dynamically typed, but every value still has a type. Walk me through the built-in data types you use day to day, how you would group them, and which of them can change after they are created."

What a strong answer should cover:

The groups: numbers (int, float, complex, bool), text and binary (str, bytes, bytearray), sequences (list, tuple, range), the mapping dict, sets (set, frozenset) and None (type NoneType).
Which are mutable (list, dict, set, bytearray) and which are immutable, and why that decides what can be a dict key (hashability).
Precise behaviour: int has arbitrary precision, float is a 64-bit IEEE 754 double (so 0.1 + 0.2 is not 0.3), bool is a subclass of int, / always returns a float.
Dynamic but strong typing: names have no type, objects do, and 1 + "1" raises TypeError instead of converting.
A CPython or version detail: dict keeps insertion order as a language guarantee since 3.7, type() vs isinstance(), or the 4300-digit int/str conversion limit.

Code / implementation expected: Optional — a few type() / isinstance() calls or a short table of literals is enough.

data-types
basics

Try it yourself

Sketch your approach before you read the solution. That is what the interview tests.

Stuck? Get a hint.

A short nudge toward the approach. It will not give the answer away.

Solution

Target Audience: Beginners preparing for Python interviews — no prior Python knowledge assumed. Difficulty: Easy Python version: Behaviour checked on CPython 3.11 (python3.11 and the in-page Pyodide 0.25.1 runtime, which is CPython 3.11.3).

How to read this doc: Each idea is explained in plain language first, then tagged with 📌 Interview term: so you also learn the exact word an interviewer expects. Every output shown in the Verified section was copied from a real run of the examples on this page.

1. Why This Even Matters — A Story First

Think of a well-organised kitchen. Flour goes in a jar, eggs in a carton, spices in a rack of small labelled tins, and leftovers in a box with a lid you can open and refill. Each container is good at one job: the egg carton keeps things in a fixed order, the spice rack lets you find "cumin" by its label, and the leftovers b

The solution is hidden so you can try first

13 min read · 10 sections

Run the code

Edit the code and run it here. Each console line with an expected value becomes a test.

PythonEvery built-in type, bool as int, big ints, floats and strong typing

Practice

PythonContainer families, hashability and the 1 / 1.0 / True dict key

Practice

Discussion

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