# VTKPythonAlgorithmBase for custom annotations
**URL:** https://discourse.paraview.org/t/vtkpythonalgorithmbase-for-custom-annotations/1939
**Category:** ParaView Support
**Tags:** python
**Created:** [May 28, 2019, 1:30pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-for-custom-annotations/1939 "2019-05-28T13:30:37Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [May 28, 2019, 1:30pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-for-custom-annotations/1939/1 "2019-05-28T13:30:37Z")
Dear devs,
Can one use the VTKPythonAlgorithmBase class to create annotation filters, i.e. show additional descriptive text? I have managed to open a table in a separate window, but never to show a text in the same window.
I have a feeling there should be a connection to the PrintSelf function and the ostream to achieve this, is it so? Any help is deeply appreciated.
Best,
Art
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [June 3, 2019, 12:53pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-for-custom-annotations/1939/2 "2019-06-03T12:53:16Z")
You may want to precise what you are trying to achieve.
---
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [June 3, 2019, 1:08pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-for-custom-annotations/1939/3 "2019-06-03T13:08:56Z")
As an execrcise, I am trying to write a PV plugin in python, that would create an annotation filter, i.e. show a text at the top of the render view window. The problem is that instead of a string I get a table in the Spread Sheet view. I also compared the python implementation with existing c++ filters, and the only thing that was different is that c++ filters have the PrintSelf function, while python filters do not.
---
### Author:  [@utkarsh.ayachit](https://discourse.paraview.org/u/utkarsh.ayachit)
#### Post date: [June 3, 2019, 1:32pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-for-custom-annotations/1939/4 "2019-06-03T13:32:05Z")
A filter indicate it’s producing data that should rendered as text by adding a hint. If your filter is producing a table with a single row/column with the string to be rendered as text in the render view, the following hint should do the trick.
```python
@smhint.xml("")
class Foo(VTKPythonAlgorithmBase):
...
```
---
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [June 11, 2019, 2:30pm UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-for-custom-annotations/1939/5 "2019-06-11T14:30:31Z")
Dear Mathieu, dear Utkarsh,
I’m sorry, but I still cannot get it right. I have added the hint as you suggested, yet I still get no text in the render view, but a table in a separate window. Here is my code:
```auto
@smproxy.filter(name="CustomAnnotationFilter",
label="CustomAnnotationFilter")
@smproperty.input(name="InputDataSet", port_index=0)
@smdomain.datatype(dataTypes=["vtkDataObject"],
composite_data_supported=False)
@smhint.xml("")
class ExampleTwoInputFilter(VTKPythonAlgorithmBase):
def __init__ (self):
VTKPythonAlgorithmBase. __init__ (self, nInputPorts=1,
nOutputPorts=1, outputType="vtkTable")
def FillInputPortInformation(self, port, info):
info.Set(self.INPUT_REQUIRED_DATA_TYPE(), "vtkDataObject")
return 1
def RequestData(self, request, inInfoVec, outInfoVec):
output = vtkTable.GetData(outInfoVec, 0)
data = vtk.vtkStringArray()
data.SetName("text")
data.SetNumberOfComponents(1)
data.InsertNextValue("this is inserted text")
output.AddColumn(data)
return 1
```
Upon loading the plugin, I create a sphere from source and apply this filter.
Once again, any help is deeply appreciated, thank you.
Art
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [June 14, 2019, 11:39am UTC](https://discourse.paraview.org/t/vtkpythonalgorithmbase-for-custom-annotations/1939/6 "2019-06-14T11:39:36Z")
Here is a Python text source that work out of the box.
```auto
@smproxy.source(name="PythonText",
label="PythonText")
@smhint.xml("")
class PythonText(VTKPythonAlgorithmBase):
"""This is dummy VTKPythonAlgorithmBase subclass that
simply puts out a Text"""
def __init__ (self):
VTKPythonAlgorithmBase. __init__ (self,
nInputPorts=0,
nOutputPorts=1,
outputType='vtkTable')
from paraview.modules.vtkPVVTKExtensionsDefault import vtkPVTextSource
self._realAlgorithm = vtkPVTextSource()
def RequestData(self, request, inInfo, outInfo):
from vtkmodules.vtkCommonDataModel import vtkTable
self._realAlgorithm.Update()
output = vtkTable.GetData(outInfo, 0)
output.ShallowCopy(self._realAlgorithm.GetOutput())
return 1
@smproperty.stringvector(name="Text")
def SetText(self, text):
self._realAlgorithm.SetText(text)
self.Modified()
```