# Extensions build error: numpy not found

**URL:** <https://discourse.slicer.org/t/extensions-build-error-numpy-not-found/13768>\
**Category:** Support\
**Created:** [September 30, 2020, 9:28am UTC](https://discourse.slicer.org/t/extensions-build-error-numpy-not-found/13768 "2020-09-30T09:28:38Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![JoostJM](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/joostjm/32/1091_2.png) [@JoostJM](https://discourse.slicer.org/u/JoostJM)\
**Post date:** [September 30, 2020, 9:28am UTC](https://discourse.slicer.org/t/extensions-build-error-numpy-not-found/13768/1 "2020-09-30T09:28:38Z")

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In the SlicerRadiomics extension, PyRadiomics is built as an external dependency. However, in the Linux build, the PyRadiomics build [fails](http://slicer.cdash.org/buildSummary.php?buildid=2025491), due to “No module named numpy”.

Numpy is needed for de setup of PyRadiomics, as it’s headers are required to build the C-extensions in PyRadiomics.

Should I add a pip command to install this dependency? I thought numpy was already part of the Slicer superbuild, and in such a way it would potentially break things if you try to re-install it.

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**Author:** ![jamesobutler](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jamesobutler/32/7511_2.png) [@jamesobutler](https://discourse.slicer.org/u/jamesobutler)\
**Post date:** [September 30, 2020, 1:22pm UTC](https://discourse.slicer.org/t/extensions-build-error-numpy-not-found/13768/2 "2020-09-30T13:22:16Z")

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Numpy should be included in the Slicer superbuild. Have you downloaded the latest Slicer preview on Linux to see if you can import numpy in the python interactor?

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<div class="post-metadata">

**Author:** ![JoostJM](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/joostjm/32/1091_2.png) [@JoostJM](https://discourse.slicer.org/u/JoostJM)\
**Post date:** [October 1, 2020, 9:16am UTC](https://discourse.slicer.org/t/extensions-build-error-numpy-not-found/13768/3 "2020-10-01T09:16:30Z")

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I will take a look. Interestingly though, this error only occurs on the 4.10 stable release. The nightly build completes without error.