What is the difference between a list and a tuple?

Q: What is the difference between a list and a tuple?

**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). Bytecode names are those of 3.11. > **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 A shopping list on your fridge and the address on an envelope both hold a few items in order. The shopping list changes all week: you add milk, cross off eggs, add bread twice. Nobody cares how long it is. The address is different: it has exactly a house number, a street, a city and a postcode, each position means something specific, and once the letter is posted it must not change. Swapp

The problem

Question presented to candidate: "Lists and tuples both hold an ordered sequence of items. What is actually different between them, and how do you decide which one to use?"

What a strong answer should cover:

The core distinction: a list is mutable (append, insert, remove, assign by index), a tuple is immutable once created.
Consequences: a tuple is hashable when its items are, so it can be a dict key or set member; a list never can. Tuple immutability is shallow.
Intent: a list is a variable-length collection of similar items; a tuple is a fixed-size record whose positions mean something (coordinates, a row, a function returning several values), and namedtuple names those positions.
Syntax traps: the comma makes a tuple, so (1) is an int and (1,) is a tuple; packing and unpacking.
CPython detail: a tuple stores its items inline with no spare capacity (smaller), the compiler folds a tuple of constants into one constant, and a list over-allocates so append is amortised O(1).

Code / implementation expected: Optional — a few lines showing mutation, a tuple as a dict key and (1,) vs (1).

python
basics

Try it yourself

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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). Bytecode names are those of 3.11.

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

A shopping list on your fridge and the address on an envelope both hold a few items in order. The shopping list changes all week: you add milk, cross off eggs, add bread twice. Nobody cares how long it is. The address is different: it has exactly a house number, a street, a city and a postc

The solution is hidden so you can try first

10 min read · 11 sections

Run the code

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

PythonMutability, the two tuple methods, the comma, dict keys and size

Practice

PythonConstant folding with dis, conversions and namedtuple

Practice

Discussion

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