Simon Willison’s Weblog

Subscribe
Atom feed for ctypes

8 items tagged “ctypes”

2024

Reviving PyMiniRacer (via) PyMiniRacer is “a V8 bridge in Python”—it’s a library that lets Python code execute JavaScript code in a V8 isolate and pass values back and forth (provided they serialize to JSON) between the two environments.

It was originally released in 2016 by Sqreen, a web app security startup startup. They were acquired by Datadog in 2021 and the project lost its corporate sponsor, but in this post Ben Creech announces that he is revitalizing the project, with the approval of the original maintainers.

I’m always interested in new options for running untrusted code in a safe sandbox. PyMiniRacer has the three features I care most about: code can’t access the filesystem or network by default, you can limit the RAM available to it and you can have it raise an error if code execution exceeds a time limit.

The documentation includes a newly written architecture overview which is well worth a read. Rather than embed V8 directly in Python the authors chose to use ctypes—they build their own V8 with a thin additional C++ layer to expose a ctypes-friendly API, then the Python library code uses ctypes to call that.

I really like this. V8 is a notoriously fast moving and complex dependency, so reducing the interface to just a thin C++ wrapper via ctypes feels very sensible to me.

This blog post is fun too: it’s a good, detailed description of the process to update something like this to use modern Python and modern CI practices. The steps taken to build V8 (6.6 GB of miscellaneous source and assets!) across multiple architectures in order to create binary wheels are particularly impressive—the Linux aarch64 build takes several days to run on GitHub Actions runners (via emulation), so they use Mozilla’s Sccache to cache compilation steps so they can retry until it finally finishes.

On macOS (Apple Silicon) installing the package with “pip install mini-racer” got me a 37MB dylib and a 17KB ctypes wrapper module.

# 24th March 2024, 5 pm / open-source, v8, python, javascript, ctypes

2022

Running C unit tests with pytest (via) Brilliant, detailed tutorial by Gabriele Tornetta on testing C code using pytest, which also doubles up as a ctypes tutorial. There’s a lot of depth here—in addition to exercising C code through ctypes, Gabriele shows how to run each test in a separate process so that segmentation faults don’t fail the entire suite, then adds code to run the compiler as part of the pytest run, and then shows how to use gdb trickery to generate more useful stack traces.

# 12th February 2022, 5:14 pm / c, ctypes, pytest

2010

ijson. A SAX-style streaming JSON parser for Python, using ctypes to talk to the yajl C library.

# 22nd September 2010, 9:59 pm / ctypes, json, python, sax, recovered

2008

django-evserver. Marek Majkowski got Comet working with Django using a custom WSGI server that wraps libevent using ctypes.

# 19th January 2008, 12:15 pm / python, django, comet, wsgi, libevent, ctypes, djangoevserver, marekmajkowski

2007

Hello JS-CTYPES, Goodbye Binary Components. Mark Finkle is porting Python’s ctypes functionality to the Mozilla platform, to allow binary XPCOM components to be defined in pure JavaScript.

# 22nd September 2007, 11:57 pm / mark-finkle, ctypes, javascript, mozilla, python, xpcom

2006

Fun with ctypes

This probably only works on Intel-based OS X machines:

[... 86 words]

What I’m excited about, post-conference edition

Wow, I’ve had a really busy month. I’ve attended (and spoken at) BarCamp London, Media in Transition, d.Construct, RailsConf Europe, Euro Foo and EuroOSCON. All were excellent, and each one nicely complemented the others. I’m exhausted. I think my brain is full.

[... 377 words]

Exciting stuff in Python 2.5

Python 2.5 alpha 1 is out, and as usual the What’s New in Python 2.5 document provides a pleasant overview of the new features. There are some real treats in there. While I’m hoping that the syntax for conditional expressions will grow on me, I’m looking forward to Partial function application becoming a common Python idiom. Relative imports are going to make Django applications a lot easier to redistribute, and I can’t wait to see all the crazy hacks that result from the introduction of coroutines.

[... 291 words]