Changelog

June 17, 2026 · View on GitHub

All notable changes to numpy-stl are documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

Unreleased

4.0.0 - 2026-06-17

Fixed

Binary STL triangle count is now read and written as the unsigned 32-bit integer the spec requires; counts with the high bit set no longer slip past the size check and silently read the whole file
The stl, stl2ascii and stl2bin commands work with piped stdin/stdout again: the std stream defaults now use the underlying binary buffers, and non-seekable streams are buffered so format auto-detection can rewind
ASCII STL output uses {:.9g} formatting: float32 values round-trip exactly instead of values below 5e-7 being flattened to 0.000000
save() no longer swallows OSErrors; write failures (disk full, broken pipe) propagate instead of silently producing truncated output
transform() now rotates the stored normals along with the vertices
translate(), transform() and rotate_using_matrix() invalidate the cached min_/max_ bounding box
remove_duplicate_polygons compares full triangles instead of per-axis vertex sums; distinct triangles with equal sums are no longer dropped
PLY reader: elements declared before vertex are skipped instead of being consumed as vertex data; scalar and extra list face properties around the vertex index list are consumed correctly; out-of-range and negative face indices raise ValueError instead of crashing or wrapping around silently
PLY reader: vertex elements with list properties raise a descriptive ValueError instead of KeyError: 'list'
3MF loader raises descriptive ValueErrors for missing vertex/triangle attributes and out-of-range vertex indices
The pure-Python ASCII reader no longer hits RecursionError on files with long runs of blank lines
Mesh.from_file() on an empty file raises a descriptive ValueError instead of TypeError
save()/load() accept plain ints for mode and validate them as Mode values
Speedups are disabled automatically on non-seekable streams for both reading and writing (the C extension requires seekable files)

Changed

get_mass_properties() docs no longer claim a RuntimeError is raised for open meshes; the actual behavior (warning + unreliable values) is documented
Publishing to PyPI is gated on the full CI test suite
numpy dependency declares the tested lower bound (numpy>=1.24)
The ASCII speedups are no longer bundled as a compiled Cython extension. Install the optional numpy-stl[fast] extra (the external speedups>=2.0.0 package) to enable them. Without it, speedups=True transparently falls back to the pure-Python reader/writer, so existing code keeps working — only the C-accelerated path now needs the extra.

Removed

Support for Python 3.9 and earlier. The minimum supported version is now Python 3.10 (requires-python = ">=3.10"); installing on older interpreters resolves to the previous release.
The bundled stl._speedups Cython extension and its _speedups.pyx source. import stl._speedups no longer works; the accelerated ascii_read/ascii_write now come from the external speedups package (see the numpy-stl[fast] extra under Changed above).