monty-compat 0.3.0

AST-based Python compatibility checker for the Monty interpreter

monty-compat

AST-based Python compatibility checker for the Monty sandbox.

Parses the Monty Rust source to extract every implemented builtin function, type constructor, exception type, and stdlib module, then checks arbitrary Python code for unsupported features — without executing it.

Installation

pip install monty-compat

Or for development (from checkout):

pip install -e .

Quick start

from monty_compat import monty_compat

# One-shot check — loads capabilities from cache (or builds on first run)
ok, reasons = monty_compat("x = [i * 2 for i in range(10)]")
# ok=True, reasons=[]

ok, reasons = monty_compat("import json; json.loads('{}')")
# ok=False, reasons=["module 'json' is not supported by Monty"]

# Force rebuild (ignores cache)
ok, reasons = monty_compat(code, cache='regenerate')

# Skip cache entirely, read from local monty checkout
ok, reasons = monty_compat(code, cache='off', monty_root='/path/to/monty')

Cache

Capabilities are cached at ~/.monty_compat/monty_{version}_compat.json.

• Default TTL: 12 hours
• Cache is version-keyed — each installed pydantic-monty version gets its own file
• cache='regenerate' forces a rebuild and overwrites the cache
• cache='off' skips all cache I/O

Lower-level API

from monty_compat import MontyCapabilities

# Build from GitHub (downloads ZIP in memory)
caps = MontyCapabilities.from_github()

# Build from a local monty repo checkout
caps = MontyCapabilities.from_local('/path/to/monty')

# Inspect capabilities
caps.builtin_functions    # frozenset: abs, all, any, bin, chr, …
caps.type_constructors    # frozenset: int, str, list, dict, …
caps.exception_types      # frozenset: ValueError, TypeError, …
caps.modules              # frozenset: sys, typing, asyncio, pathlib, os, re, …
caps.module_attributes    # dict:      {'asyncio': {'gather', 'run'}, …}

# Check code
ok, reasons = caps.check_code(some_code)

# Pretty-print
print(caps.summary())

What is checked

Pattern	Example	Check
import X	import json	Is json a supported module?
from X import Y	from asyncio import subprocess	Is Y in X's known attributes?
Builtin calls	eval(...)	Is the builtin implemented in Monty?

Supported modules (as of 2026-03)

Module	Available attributes
re	search, match, sub, findall, …
asyncio	gather, run
os	getenv, environ
pathlib	Path
sys	platform, version, version_info, stdout, stderr
typing	Any, Optional, Union, List, Dict, Callable, …