From FreeCAD Documentation


PythonOCC is a project that aims at providing the entire range of OpenCASCADE Technology (OCCT) functions through the Python module OCC. This is a different approach from FreeCAD's, where only certain components of OCCT are exposed through the Part Workbench.

PythonOCC, on the other hand, provides access to all OCCT classes and functions so it is complex but also very powerful. Therefore, when you are limited by FreeCAD's OCCT functionality, using OCC is a good alternative.


The Part Workbench has the methods Part.__toPythonOCC__() and Part.__fromPythonOCC__() to exchange TopoDS_Shape (Part TopoShape) entities to and from PythonOCC. These methods allow us to use the full power of OCCT in Python and then put the resulting shapes back into FreeCAD objects.

PythonOCC is internally used by the IFC viewer included with the IfcOpenShell libraries. IfcOpenShell is used to read and write IFC documents with FreeCAD. PythonOCC is only needed to launch IfcOpenShell's integrated viewer, otherwise it is not necessary.


PythonOCC must be compiled from source. For this you need to get the corresponding development files for OpenCASCADE Technology (OCCT) and SWIG. The older version of PythonOCC was intended to wrap around OCE 0.18, the community edition of OCCT 6.9.x, which is now unmaintained. The newest version of PythonOCC is now intended to work with the recent, official OCCT 7.4 version.

Together with OCCT 7.4, PythonOCC requires fairly recent dependencies like Python 3.7, CMake 3.12, and SWIG 3.0.11. Python 2 is no longer supported.

It is also possible to install pre-compiled PythonOCC libraries using Conda. For more information and compilation instructions, see the main project's repository, tpaviot/pythonocc-core.


You can also self compile pythonOCC (see instructions). Below is the procedure for Debian/Ubuntu using distro-provided opencascade packages:

git clone git:// pythonocc
cd pythonocc
mkdir build
cd build
cmake -DOCE_INCLUDE_PATH=/usr/include/opencascade -DOCE_LIB_PATH=/usr/lib/x86_64-linux-gnu ..

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