# VTKPythonAlgorithmBase smproperty.stringvector callback modification action
**URL:** https://discourse.paraview.org/t/vtkpythonalgorithmbase-smproperty-stringvector-callback-modification-action/9239
**Category:** Development
**Tags:** python
**Created:** [March 21, 2022, 5:31pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-smproperty-stringvector-callback-modification-action/9239 "2022-03-21T17:31:41Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@lou75](https://discourse.paraview.org/u/lou75)
#### Post date: [March 21, 2022, 5:31pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-smproperty-stringvector-callback-modification-action/9239/1 "2022-03-21T17:31:41Z")
Hi,
for a VTKPythonAlgorithmBase panel, is there a way to declare a callback function for an smproperty.stringvector upon a modification action ?
thanks for help
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### Author:  [@utkarsh.ayachit](https://discourse.paraview.org/u/utkarsh.ayachit)
#### Post date: [March 21, 2022, 5:57pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-smproperty-stringvector-callback-modification-action/9239/2 "2022-03-21T17:57:11Z")
Is that much different than what these examples do for things like [FileName](https://gitlab.kitware.com/paraview/paraview/-/blob/master/Examples/Plugins/PythonAlgorithm/PythonAlgorithmExamples.py#L258). It’s not a callback in the conventional sense, but that’s the function that will get called when the user hits `Apply` button.
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### Author:  [@lou75](https://discourse.paraview.org/u/lou75)
#### Post date: [March 21, 2022, 6:17pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-smproperty-stringvector-callback-modification-action/9239/3 "2022-03-21T18:17:24Z")
Thanks for the reply,
no unfortunately, I need the value befor the user hits the apply button
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### Author:  [@utkarsh.ayachit](https://discourse.paraview.org/u/utkarsh.ayachit)
#### Post date: [March 21, 2022, 6:24pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-smproperty-stringvector-callback-modification-action/9239/4 "2022-03-21T18:24:10Z")
That’s not supported for a `VTKPythonAlgorithm`.
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### Author:  [@lou75](https://discourse.paraview.org/u/lou75)
#### Post date: [March 21, 2022, 6:34pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-smproperty-stringvector-callback-modification-action/9239/5 "2022-03-21T18:34:41Z")
Thanks