Something wrong with OpenCascade in pip package

[conorbergin]

Python 3.13.7 (main, Aug 15 2025, 12:34:02) [GCC 15.2.1 20250813] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import netgen.stl
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    import netgen.stl
  File "/home/conor/Documents/ngsolve/.venv/lib/python3.13/site-packages/netgen/stl.py", line 1, in <module>
    from netgen.libngpy._stl import *
ImportError: libTKOffset.so.7.8.1: cannot open shared object file: No such file or directory
>>> 

[ChrLackner]

What kind of setup do you have? Win/Linux/Mac? Global installation or virtual environment?

[conorbergin]

Arch Linux, Python 13.7 venv, the ngsolve package is also not working with the same error (libTKOffset not found).

[iicurtis]

I am also seeing this issue, Arch Linux with uv venv.

> python --version
Python 3.14.2

pyproject.toml

    "netgen-mesher>=6.2.2506.post50.dev0",
    "ngsolve>=6.2.2506.post216.dev0",

I'm not sure if it matters to the venv, but system provided TKOffset is a higher version:

> fd libTKOffset /usr
/usr/lib/libTKOffset.so.7.9.3

There appears to be a libTKOffset.so provided in the venv, but it does not appear to be detected by the package.

> fd -HI libTKOffset  .venv
.venv/lib/libTKOffset.so.7.8.1

I can set LD_LIBRARY_PATH=/tmp/.venv/lib, but then other fails occur:

Traceback (most recent call last):
 File "/tmp/test.py", line 3, in <module>
 from ngsolve import *
 File "/tmp/.venv/lib/python3.14/site-packages/ngsolve/__init__.py", line 40, in <module>
 from netgen import Redraw, TimeFunction
ImportError: cannot import name 'Redraw' from 'netgen' (unknown location)

[iicurtis]

Yet it works in a fresh archlinux docker image with uv installed.

pacman -S python-uv

Something else about the install/setup appears to break this, but I have no idea where to start debugging. ldd on both the docker image and desktop fail to resolve most libs.

[ChrLackner]

Is it possible that you installed the python package netgen instead of netgen-mesher?

They are in conflict and installing both messes everything up...
It helps then to uninstall both (or setup a fresh venv) and only install netgen-mesher