# Programmable Filter: if else statment

**URL:** https://discourse.paraview.org/t/programmable-filter-if-else-statment/7514
**Category:** ParaView Support
**Created:** [June 29, 2021, 7:39pm UTC](https://discourse.paraview.org/t/programmable-filter-if-else-statment/7514 "2021-06-29T19:39:11Z")
**Posts on this page:** 1
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### Author: ![mwestphal](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mwestphal/32/17_2.png) [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [June 30, 2021, 7:25am UTC](https://discourse.paraview.org/t/programmable-filter-if-else-statment/7514/2 "2021-06-30T07:25:08Z")

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> [@Operations on multi-block dataset with Programmable Filter](https://discourse.paraview.org/t/operations-on-multi-block-dataset-with-programmable-filter/1027/6):
>
> Ah, indeed. The usual numpy functions do not work for VTKCompositeDataArrays that are available from multiblock datasets, but the numpy-like algorithms provided by vtk.numpy\_interface.algorithms do. However, the where function provided in vtk.numpy\_interface.algorithms is only the single-argument version, not the three-argument version I suggested, so merging the blocks is the only way to use this numpy expression currently.

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