Python playground

Real CPython 3.14 in your browser, for the arithmetic of networks: subnets, masks, EUI-64, DNS headers in struct, HMAC, latency statistics, transfer times. A 13.5 MB engine downloads once, when you say so; nothing you type leaves the page.

Documentation (Markdown)

Operations & FieldcraftWebAssemblyPyodide 314.0.7 (Python 3.14.2) · 13.5 MB on first use

Documentation

A WebAssembly tool

What runs: Pyodide 314.0.7, which is CPython 3.14.2 compiled to WebAssembly by the Pyodide project, under the MPL-2.0 licence. It is a real interpreter, not an imitation of one.
Where it comes from: the same origin as this page, pinned by version and by SHA-256 digest at build time. No third-party server is contacted at run time.
What the first use costs: about 13.5 MB, downloaded only when you press the button that names the size. Your browser caches it; the second visit costs nothing.
What leaves the page: nothing. The program and its input stay in a Web Worker on your device. The interpreter has no network and no processes; the page policy would refuse them anyway.
What the site's own checks cover: the harness around the engine, the examples (re-run through the real engine at every build), the preflight and the limits. The interpreter's own behaviour is its project's.

Program

# Split a /24 into /26 subnets and list what each one holds.
import ipaddress

net = ipaddress.ip_network("10.20.30.0/24")
print(f"{net}: {net.num_addresses} addresses, {len(list(net.hosts()))} usable")
for sub in net.subnets(new_prefix=26):
    hosts = list(sub.hosts())
    print(f"  {sub}  mask {sub.netmask}  hosts {hosts[0]}-{hosts[-1]}  broadcast {sub.broadcast_address}")

Python 3.14 standard library only; no packages in this version. Up to 20000 characters. The value of the last expression is shown as the result, as in a REPL.

Standard input (what input() and sys.stdin read, one line per line)

Examples:

Python playground

A WebAssembly tool

References