whatsnewt

A TUI text adventure through what's new in Python 3.15.

You wake up in the Startup Foyer, somewhere inside the interpreter, and work your way to the Release Gate. Along the way there are eighteen puzzles, and every one of them is a real 3.15 feature you have to actually use. You do not answer multiple choice questions about lazy imports; you write lazy import json in a code editor and the game checks that the name really did hold a proxy until something read it.

The exception is the Typing Sanctum, where the features are about what a type checker sees and running the code proves nothing: PEP 800 marks a class as a disjoint base and the interpreter still combines it quite happily. Those answers go to pyrefly, which is a dependency for exactly that reason, and the verdict quotes what it says back.

┌─ The Hall of Imports ──────────────────┬─ Progress ─────────────────────────┐
│ A hall the size of a cathedral, stacked│ Score    40 / 375                  │
│ to the vaulting with packages.  The    │ Puzzles  2 / 18                    │
│ moment anyone steps through the door,  │ Sigils   2 / 6                     │
│ every lid in the building flies open at│ Rooms    7 / 15                    │
│ once...                                ├─ Carrying ─────────────────────────┤
│                                        │ * the lazy lantern                 │
│ Puzzle: The packages that open         │ * the frozen seal                  │
│ themselves (PEP 810)                   ├─ Map ──────────────────────────────┤
│                                        │                ?                   │
│ > solve                                │   Crypt   -  Loop↓        ?        │
│                                        │                |                   │
│                                        │     ?       Gardens       ?        │
│                                        │                |                   │
│                                        │   Vault   ->Imports< -  Babel↑     │
│                                        │                |                   │
│                                        │              Foyer        ?        │
└────────────────────────────────────────┴────────────────────────────────────┘

Running it

$ ./play

That is a uv run shim. It fetches CPython 3.15 if that version isn't installed on your path, installs this checkout and its dependencies into a cached environment, and starts the game -- no virtual environment to create and nothing to activate first. It works from any directory, and it installs the checkout editable, so it runs your working tree rather than a snapshot of it.

Without a checkout:

$ uvx --python 3.15 whatsnewt

That runs straight from PyPI.

Useful flags, passed straight through by ./play:

Tab completes at the prompt: verbs first, then whatever the verb can take here -- ex<tab> gives examine, and examine st<tab> finds the staircase if this room has one. Ambiguous prefixes fill in as far as they agree and then show you the choice.

It needs Python 3.15

Since almost every puzzle is checked by running your answer against the feature it is about (such as : frozendict is the real built-in, math.integer is the real module, and the lazy-imports puzzle confirms the name really did hold a types.LazyImportType proxy until something read it) you actually need Python 3.15. A pre-release is acceptable.

Note that reading your source is still part of how answers are checked, and always will be: most of these puzzles have a boring answer that produces the right value the old way, so the checker looks at how you got there as well as what you got. A nested for loop that flattens correctly is still not what PEP 798 is for.

Commands

look north/n examine <thing> take drop inventory solve hint map score save load quit — and help for the rest.

Keys follow Emacs where Emacs has an opinion: ctrl+g aborts whatever is open, ctrl+h is help, ctrl+l re-shows the room, ctrl+r opens a puzzle — and checks your answer once you are inside it. The function keys still work, and every one of them is a command you can type instead.

Inside the editor: ctrl+r checks your answer, ctrl+h buys a hint for a point, ctrl+o hands the draft to $EDITOR and takes back whatever you save, and ctrl+g closes the window, keeping your draft for next time.

ctrl+o only suspends the game for editors that need the terminal. If yours opens a window of its own — emacsclient, code --wait, subl -w — the game stays up while you type, and takes the draft back when you save. Set WHATSNEWT_EDITOR_WINDOWED=1 (or =0) if the guess is wrong for yours.

Saving

The game saves itself after anything that changes it, so quitting, closing the terminal or losing the window costs you nothing — including whatever you had half-written in a puzzle editor. It writes to $XDG_STATE_HOME/whatsnewt/, falling back to ~/.local/state/whatsnewt/, rather than the working directory, since ./play deliberately runs from anywhere.

Start it again and it offers to resume your game. Declining doesn't throw it away: the old game is moved to previous-game.json beside it, so a mis-click is recoverable. save <file> and --load FILE still work for games you want to keep by name.

What it covers

Souvenirs lying around the place cover the rest: abi3t, Unicode 17 and grapheme clusters, slice[int], zlib.crc32_combine, the colored REPL completer.

Development

$ uv venv --python 3.15 && uv pip install -e '.[dev]'
$ pytest

The tests check that every puzzle rejects its own unedited starter, accepts the reference answer in tests/solutions.py, and survives being handed an empty string or something that is not Python at all. There is a full playthrough that walks every room, solves all eighteen and arrives at a perfect score, and the Textual front end is driven headlessly through Pilot rather than mocked. tests/test_shim.py keeps ./play, pyproject.toml and the version guard from disagreeing about which Python this needs.

tests/solutions.py doubles as the walkthrough, if you would rather read than play.

Everything the game teaches is answerable from Doc/whatsnew/3.15.rst.

Author

whatsnewt is Copyright (C) 2026 Barry Warsaw barry@python.org

Licensed under the terms of the Apache License Version 2.0. See the LICENSE file for details.

The game was largely co-written with Claude, so maybe Barry should be considered a Director or Producer in the music and film sense of the word. The game has been test run by Barry and several prominent Pythonistas before its release.

Project details

• Project home: https://gitlab.com/flufl/whatsnewt
• Report bugs at: https://gitlab.com/flufl/whatsnewt/-/work_items
• Code hosting: https://gitlab.com/flufl/whatsnewt.git
• PyPI: https://pypi.python.org/pypi/whatsnewt