# Compiling custom VTK extension with python wrapper
**URL:** https://discourse.vtk.org/t/compiling-custom-vtk-extension-with-python-wrapper/6427
**Category:** Support
**Created:** [August 19, 2021, 10:28am UTC](https://discourse.vtk.org/t/compiling-custom-vtk-extension-with-python-wrapper/6427 "2021-08-19T10:28:24Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Korijn](https://discourse.vtk.org/u/Korijn)
#### Post date: [August 19, 2021, 10:28am UTC](https://discourse.vtk.org/t/compiling-custom-vtk-extension-with-python-wrapper/6427/1 "2021-08-19T10:28:24Z")
I am working to compile a [custom VTK extension](https://github.com/ClinicalGraphics/u3d/tree/master/Samples/SampleCode) with python wrappers, and am trying to figure out how to do it with the new VTK 9 cmake build system.
I must admit I am in a little bit over my head, and am hoping to receive some general guidance and/or references to other projects that have to overcome the same challenges. Any tips?
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### Author:  [@dgobbi](https://discourse.vtk.org/u/dgobbi)
#### Post date: [August 19, 2021, 12:59pm UTC](https://discourse.vtk.org/t/compiling-custom-vtk-extension-with-python-wrapper/6427/2 "2021-08-19T12:59:26Z")
In VTK 9, wrapping is done on a per-module basis, so the code that is to be wrapped must be arranged so that VTK can see it as a “module”, e.g.:
```bash
CMakeLists.txt # the cmake file that calls the cmake module macros
YourModule/ # the module directory
vtk.module # the "module file", contains info about the module
CMakeLists.txt # the module's CMakeLists.txt file
vtkSomeClass.h # a header to be wrapped
vtkSomeClass.cxx
...
```
A sample can be found in [Examples/Modules/Wrapping](https://gitlab.kitware.com/vtk/vtk/-/tree/master/Examples/Modules/Wrapping/module).