Run Python 3.15 online

What's in Python 3.15

• Currently 3.15.0rc — pinned to the upstream release-candidate build for early feedback.
• PEP 750 tail-call interpreter default on more platforms; measurable win on interpreter-heavy code.
• Continued no-GIL maturation from 3.14: fewer stdlib fallbacks, better free-threaded ergonomics.

What you get in Python 3.15

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 3.15

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 3.15toolchain 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.