Python

Computerwelt.Emulation.Python is a Python implementation in C#: a parser, a bytecode compiler with scope and name resolution, a stack VM with its own object heap, the built-in types, the built-in functions, and a subset of the standard library.

It is a port of Monty, which Pydantic built for exactly this job: running code a language model wrote, safely, without a CPython process.

using Computerwelt.Emulation.Python;

var runner = new PythonRunner();

var result = runner.Run("""
    rows = [{"id": i, "sq": i * i} for i in range(4)]

    for row in rows:
        print(row["id"], row["sq"])
    """);

Console.WriteLine(result.Stdout);

RunResult

A failure is a value here, not a .NET exception. That is what lets a host feed a traceback back to a model as ordinary text.

Configuring a run

var runner = new PythonRunner(ExecutionLimits.Strict)
{
    Arguments     = { "report", "--json" },   // sys.argv
    StandardInput = "42\n",                   // sys.stdin
};

runner.Variables["threshold"] = new PyInt(10);   // a pre-set global

var result = runner.Run(source, fileName: "report.py");

FileSystem and TimeProvider are settable too, so a program's open, os and clock are whatever the host decided they are. Leave the filesystem unset and the program has none: open raises OSError, which is an error the script can catch rather than a host exception escaping into it.

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