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Monty

Runs code in Monty, a minimal, secure Python interpreter written in Rust (pydantic-monty). Monty runs a restricted subset of Python in-process with microsecond startup and no access to the host filesystem, environment, or network unless explicitly granted. It is ideal for short, LLM-generated snippets where a full container or kernel would be overkill.

Session state (variables, imports, definitions) persists across run_code calls. Note that Monty supports only a subset of Python — third-party libraries and rich display outputs are not available.

  • Requirements: code-sandboxes[monty] (installs pydantic-monty).
  • Credentials: none required (fully local, in-process).
  • Optional parameters (on MontySandbox): type_check (type-check before running), type_check_stubs, external_functions ({name: callable} host functions the code may call), limits (memory / stack / time limits).

Usage​

from code_sandboxes import Sandbox

with Sandbox.create(variant="monty") as sandbox:
    sandbox.run_code("x = 21")
    result = sandbox.run_code("x * 2")
    print(result.text)  # 42

Host Callables And Type Checking​

You can expose host callables to the sandboxed code and enable type checking:

from code_sandboxes.monty_sandbox import MontySandbox

sandbox = MontySandbox(
    type_check=True,
    external_functions={"now": lambda: "2026-01-01"},
)
sandbox.start()
sandbox.run_code("print(now())")