Run Python 3.12 online

What's in Python 3.12

• PEP 695: cleaner generic-type syntax (`def first[T](l: list[T]) -> T:`).
• PEP 701: f-strings finally have a real grammar — you can nest quotes inside them freely.
• Per-interpreter GIL groundwork (PEP 684) lands as a private API.

What you get in Python 3.12

Clicking "Run now" opens the playground with this exact code and a matching test case — passes on first Run.

n = int(input())
print(n * 2)

How ls-judge runs Python 3.12

Every submission is compiled and executed inside its own Firecracker microVM — the same isolation primitive AWS Lambda uses. No shared container, no shared kernel with other users' code. The Python 3.12toolchain shipped with the microVM is the real thing (not a browser-side emulation): syscalls behave the way they do in production, and the compile / runtime behaviour matches what you would see on your own machine with that version installed.

Feed stdin from the Tests panel, watch verdicts stream per test case over a WebSocket. Free to use, no sign-up, works from any browser.