# How to write an adaptor for legacyvtk data format in Paraview Catalyst
**URL:** https://discourse.paraview.org/t/how-to-write-an-adaptor-for-legacyvtk-data-format-in-paraview-catalyst/4025
**Category:** ParaView Support
**Tags:** python
**Created:** [April 10, 2020, 7:37pm UTC](https://discourse.paraview.org/t/how-to-write-an-adaptor-for-legacyvtk-data-format-in-paraview-catalyst/4025 "2020-04-10T19:37:47Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@leoncwu](https://discourse.paraview.org/u/leoncwu)
#### Post date: [April 10, 2020, 7:37pm UTC](https://discourse.paraview.org/t/how-to-write-an-adaptor-for-legacyvtk-data-format-in-paraview-catalyst/4025/1 "2020-04-10T19:37:47Z")
I am still struggling with writing my own adaptor for data in legacyvtk format. I found 2 examples written in Python, which is of my interest.
Example 1: can crash
`input_ds = pvsimple.ExodusIIReader( FileName=[sys.argv[2]])`
`input_ds.ElementVariables = ['EQPS']`
`input_ds.EdgeBlocks = []`
`input_ds.GlobalVariables = ['KE', 'XMOM', 'YMOM', 'ZMOM', 'NSTEPS', 'TMSTEP']`
`input_ds.ElementBlocks = ['Unnamed block ID: 1 Type: HEX', 'Unnamed block ID: 2 Type: HEX']`
`input_ds.PointVariables = ['DISPL', 'VEL', 'ACCL']`
`input_ds.FaceBlocks = []`
`timeArray = input_ds.TimestepValues`
`for step in range(len(timeArray)):`
`time = input_ds.TimestepValues[step]`
`input_ds.UpdatePipeline(time)`
`dataset = input_ds.GetClientSideObject().GetOutputDataObject(0)`
`# "perform" coprocessing. results are outputted nly if`
`# the passed in script says we should at time/step`
`coProcess(dataset, time, step, sys.argv[1])`
Example 2: wavelet
`pm = pvsimple.servermanager.vtkProcessModule.GetProcessModule()`
`rank = pm.GetPartitionId()`
`nranks = pm.GetNumberOfLocalPartitions()`
`for step in range(numsteps):`
` # assume simulation time starts at 0`
` time = step/float(numsteps)`
` print("[%d/%d]: Timestep %d of %d (time=%f)" % (rank, nranks, step, numsteps, time))`
` # create the input to the coprocessing library. normally`
` # this will come from the adaptor`
` wavelet = pvsimple.Wavelet()`
` wholeExtent = wavelet.WholeExtent`
` # put in some variation in the point data that changes with time`
` wavelet.Maximum = 255+200*math.sin(step * math.pi / 100)`
` wavelet.UpdatePipeline()`
` imageData = pvsimple.servermanager.Fetch(wavelet)`
` # note that we delete wavelet now since. if not, it will`
` # get deleted automatically in the coprocessing script`
` pvsimple.Delete(wavelet)`
` wavelet = None`
` # "perform" coprocessing. results are outputted only if`
` # the passed in script says we should at time/step`
` coProcess(imageData, time, step, sys.argv[1], wholeExtent)`
` imageData = None`
` import time`
` time.sleep(1)`
I got the point that the results from the simulation will be transferred to Paraview by the “coProcess(data, time, step, coprocessing\_file, …)” function. My question is how the first argument “data” looks like. What is the structure of the data (or data class)? I am a little confused since the given examples pass the results all in different formats. Example 1 uses a method in the classExodusIIReader - GetClientSideObject().GetOutputDataObject(0), which I did not find it in the class description ([https://kitware.github.io/paraview-docs/latest/python/paraview.simple.ExodusIIReader.html](https://kitware.github.io/paraview-docs/latest/python/paraview.simple.ExodusIIReader.html)). Example 2 uses the server manager to extract the results - pvsimple.servermanager.Fetch(wavelet). I tried to search and dig into the source code to find possible similarities or hints, but I could not find the information I need.
In my case, the results are in vtk format. I presume I should use the LegacyVTKReader to load the results, which is most similar to the situation in example 1. What about next? Are there any methods I could use to convert/process the results so that the function “coProcess” can take it and pass it to Paraview?
Sorry for so many questions. I am actually a beginner of both Python and Paraview. I planed to upload the files of the can crash case, but it was too big to be accepted by the browser. BTW, I attached the wavelet source code again to this post in case you need more information. Looking forward to your reply.
[CatalystWaveletCoprocessing.py](https://discourse.paraview.org/uploads/short-url/3wjupQ1mMOAVss9KJssSnFY37kt.py) (3.1 KB)
[CatalystWaveletDriver.py](https://discourse.paraview.org/uploads/short-url/vM0KzbOXaXVvsDcD064JIbhQJaC.py) (3.3 KB)
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [April 14, 2020, 3:34am UTC](https://discourse.paraview.org/t/how-to-write-an-adaptor-for-legacyvtk-data-format-in-paraview-catalyst/4025/2 "2020-04-14T03:34:24Z")
(Just a quick note about your formatting, please use the whole block of code formatting style instead of line by line formatting)