What is the difference between __repr__ and __str__?

Q: What is the difference between __repr__ and __str__?

**Target Audience:** Beginners who have written a class or two, up to intermediate developers revising for interviews. **Difficulty:** Easy **Python version:** Behaviour checked on CPython 3.11 and 3.13 (identical output); every example also runs in the page on Pyodide 0.25.1 (CPython 3.11.3). > **How to read this doc:** Each idea is explained in plain language first. When a word appears that an interviewer expects you to know, it is tagged with `📌 Interview term:` and defined right there. All of them are collected in the Quick Glossary at the end. Every output shown was produced by actually running the code. ## 1. Why This Even Matters — A Story First A bakery prints two labels for every cake. The one stuck on the box for the customer says "Chocolate cake — 12.00 EUR". The one on the order slip in the kitchen says "order 4471, recipe CHOC-2, 8 inch, no nuts, baked 07:15". Same cake, two audiences. The customer wants something pleasant to read. The baker wants every detail needed t

The problem

Question presented to candidate: "Python classes can define both __repr__ and __str__. What is the difference between them, when does Python call each one, and if you only had time to write one, which would it be?"

What a strong answer should cover:

__str__ is the readable, end-user text (print(x), str(x), f"{x}"); __repr__ is the unambiguous, developer-facing text (repr(x), the REPL, debuggers, logs).
Containers such as lists and dicts show the repr of their elements, even when you print the container.
The fallback rule: if __str__ is missing, str() uses __repr__; the reverse is not true, so __repr__ is the one to write first.
Convention: for simple value types repr looks like a constructor call, ideally so that eval(repr(x)) == x; otherwise use the <ClassName ...> style.
!r and the f"{x=}" debugging form (Python 3.8+) use repr; both methods must return a str.
dataclasses generate __repr__ for you; reprlib.recursive_repr guards self-referencing objects.

Code / implementation expected: Yes — a small class with both methods, showing print, repr, a list of the objects and an f-string with !r.

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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 who have written a class or two, up to intermediate developers revising for interviews. Difficulty: Easy Python version: Behaviour checked on CPython 3.11 and 3.13 (identical output); every example also runs in the page on Pyodide 0.25.1 (CPython 3.11.3).

How to read this doc: Each idea is explained in plain language first. When a word appears that an interviewer expects you to know, it is tagged with 📌 Interview term: and defined right there. All of them are collected in the Quick Glossary at the end. Every output shown was produced by actually running the code.

1. Why This Even Matters — A Story First

A bakery prints two labels for every cake. The one stuck on the box for the customer says "Chocolate cake — 12.00 EUR". The one on the order slip in the kitchen says "order 4471, recipe CHOC-2, 8 inch, no nuts, baked 07:15". Same cake,

The solution is hidden so you can try first

9 min read · 11 sections

Run the code

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

PythonMoney: str for users, repr for developers, and the fallback rule

Practice

PythonBuilt-ins, dataclasses, recursive reprs and reprlib

Practice

Discussion

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What is the difference between repr and str?