Small Python
Small Python is a small and embeddable Python runtime. This package,
small-python, runs it from CPython: create isolated interpreters, run code in
them, and give that code exactly the functions, modules, and files you choose.
Features
- Small, just a few C files, no external dependencies.
- No Python Libs. Attach your own modules.
- Almost complete Python 3.15 support.
- Run code generated by AI against only the functions you expose.
- Each runtime runs in its own worker process: an engine crash raises an exception instead of taking down your program.
- Limits on steps, memory, time, and message size.
- Can compile Python code to executables with no external dependency.
- GC uses reference counting with cycle removal.
Install
pip install small-python
Requires CPython 3.10 or newer on Linux, macOS, or Windows (x86_64).
Example
import small_python
with small_python.Runtime(step_limit=1_000_000, memory_limit=64 << 20, timeout=5) as rt:
@rt.function
def fetch(key, *, default=None):
return {"answer": 42}.get(key, default)
rt.register_module("host", {"fetch": fetch}, source="def twice(n): return n * 2")
rt.exec("from host import twice")
print(rt.eval("twice(fetch('answer'))")) # 84
Documentation
- Getting started
- Embedding guide: host functions, modules, output, files, errors
- Limits and safety
- API reference
- Development: building, testing, and releasing
Build
Requires a C11 compiler. Manage the project with uv:
uv sync --locked
uv run python -c "import small_python"
uv build
See Development for tests and the release process.
1 maintainer
Metadata
1 maintainer
Release files for small-python 0.3.0
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Source distribution (sdist)
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|---|---|---|---|---|
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Built distributions (wheels)
Total release size: 11.2 MB
Release files / small_python-0.3.0.tar.gz
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