Geoffrey Thomas geofft

Deprecating the assumption that libpython is dynamically linked

Hi! When we switched python-build-standalone to statically linking libpython into bin/python, we ran into some code that made assumptions that libpython was dynamically linked and expected to be able to open libpython3.x.so.1 and have that be the running libpython. We had to introduce some poor workarounds for such code. I want to propose that CPython actively monitor for this assumption and raise DeprecationWarnings with the intention of breaking such code in the future.

As background, the Python interpreter executable, which I'll call "bin/python", is a short C program that just calls Py_BytesMain(argc, argv). The actual Python runtime is in libpython, which can be either statically or dynamically linked into bin/python. Static linking is better for performance, especially on the free-threaded build for reasons involving thread-local storage access, which is why we switc

Miscellaneous church music

Thomas Tallis, "If Ye Love Me"
- SATB, one page
SATB with piano reduction, 3 pages

dataenum

This is a combination of @dataclass and enum.Enum, inspired by https://blog.glyph.im/2025/01/active-enum.html . I didn't like that the syntax required making two classes, and naively combining @dataclass on an enum.Enum doesn't work (and is documented as such in the standard library docs).

The key insight is that all dataclass fields must be typed, and all enum members should not be typed, so we can unambiguously write something like this:

@dataenum
class SomeNumber:
 result: int

main.cc: A very abbreviated version of chapter 3 of the LLVM tutorial, hard-coding a single function
main.py: A translation into Python using llvmlite, also hard-coding a main function
pycomp.py: A compiler for an extremely small subset of Python.

$ ../venv/bin/python3 pycomp.py < sourcecode.py
$ cc -o output output.o
$ ./output
24.000000

Quick setup instructions for building the code from Sy Brand's Building a Debugger on a machine with a working Nix installation. (There are many other perfectly good ways to get set up; if you don't already have Nix you might prefer to do something else.)

For Recursers, you can get to a machine with Nix by configuring your SSH key, waiting an hour or two, and doing ssh broome.cluster.recurse.com.

The author's worked source code is available on GitHub, so if you want to start partway through the book, do e.g.

git clone https://github.com/TartanLlama/sdb -b chapter-8
cd sdb

	#!/usr/bin/env python3
	#
	# Use VS Code themes on the Linux VT (text mode) console. I use this with the themes from
	# https://github.com/liviuschera/noctis
	# Usage:
	# 1) Download a theme JSON file
	# 2) python vscode-theme-to-linux-vt.py theme.json \| sh
	# - or -
	# 2) python vscode-theme-to-linux-vt.py theme.json > theme.sh
	# 3) chmod +x theme.sh

	#!/usr/bin/env -S uv run
	# /// script
	# requires-python = ">=3.14"
	# dependencies = [
	# "html5lib",
	# "httpx",
	# ]
	# ///

	import lzma

	FROM python:3.12-slim-bookworm
	COPY --from=ghcr.io/astral-sh/uv:latest /uv /uvx /bin/
	RUN uv venv /v
	WORKDIR /v
	RUN env UV_TORCH_BACKEND=auto uv pip install torch numpy
	CMD /bin/bash

	{'_PyEval_StartTheWorldAll', 'bio_sock_cleanup_int', 'AtForkPrepare', 'TclInitNamespaceSubsystem', 'ossl_comp_zlib_cleanup', 'ossl_trace_cleanup', '_PyEval_StopTheWorldAll', 'AtForkParent'}
	{'PyLzma_Free', 'BZ2_Free', 'PyZlib_Free'}
	{'mbstreamwriter_init', 'OSSL_trace_set_channel', 'mbidecoder_init', 'never_optimize', 'mbstreamreader_init', 'mbiencoder_init', 'ERR_func_error_string', 'PyExec_faulthandler'}
	{'EVPXOF_get_digest_size', 'long_get0'}
	{'EVP_KDF_free', 'evp_kdf_free'}
	{'EVP_KDF_up_ref', 'evp_kdf_up_ref'}
	{'evp_md_free', 'EVP_MD_free'}
	{'evp_md_free.cold', 'EVP_MD_free.cold'}
	{'bytearray_length', 'deque_len', 'array_length', 'mpd_getemin', 'list_length', 'dict_length', 'bytes_length', 'tuplelength', 'unicode_length', 'EVP_MD_get_flags'}
	{'EVP_MD_up_ref', 'evp_md_up_ref'}

	*.so
	nixpkgs-*