Scripting FreeCAD from an AppImage

Appimages are yet another, honestly the number of these is insane, packaging methods for distributing code with all dependencies included. It’s one of the simpler approaches, there’s no package manager for it, you download the image and go. The FreeCAD AppImages (here) work great and is my typical approach to installation.

One of FreeCADs strengths is the scripting interface. The GUI maps button clicks to commands meaning you can script everything out of the gate (mostly, it’s better than most). AppImages make this only a bit more complicated than native installations.

Credit to Stack Overflow user tompi for the guide: https://stackoverflow.com/questions/67325416/how-to-embed-freecad-in-a-python-virtual-environment

1. Extract the appimage into a known location:

> mkdir ${HOME}/.FreeCAD
> cd ${HOME}/.FreeCAD
> FreeCAD_0.20-1-2022-08-20-conda-Linux-x86_64-py310.AppImage --appimage-extract

2. Add FreeCAD.so to the path:

> PYTHONPATH=${PYTHONPATH}:${HOME}/.FreeCAD/squashfs-root/usr/lib

FreeCAD.so is compiled as a CPython library so is imported exactly like a normal module. This tripped me up when getting going with the paths.

3. Use the FreeCAD python interpreter to make calls:

> ${HOME}/.FreeCAD/squashfs-root/usr/bin/python -c "print('Hello World')"
Hello World

4. Link other python libraries by extending the PYTHONPATH. Here I have a virtual environment setup for FreeCAD where I install packages to use with FreeCAD.

> PYTHONPATH=${PYTHONPATH}:${HOME}/.freecad_venv/lib/python3.8/site-packages

One project I’ve built with this makes an SVG into an object which can be used as a cutting tool or embedded into a part. It makes visualization easy and allows rendering the object using the render workbench. There will probably be a write-up coming for that. https://github.com/snhobbs/inkscape-freecad-labels

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