# Python plugin failing to load in script using paraview.simple.LoadState(), but works fine in GUI

**URL:** https://discourse.paraview.org/t/python-plugin-failing-to-load-in-script-using-paraview-simple-loadstate-but-works-fine-in-gui/7960
**Category:** ParaView Support
**Created:** [September 8, 2021, 8:43pm UTC](https://discourse.paraview.org/t/python-plugin-failing-to-load-in-script-using-paraview-simple-loadstate-but-works-fine-in-gui/7960 "2021-09-08T20:43:00Z")
**Posts on this page:** 6
**Page:** 1

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### Author: ![csniker](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/c/c4cdca/32.png) [@csniker](https://discourse.paraview.org/u/csniker)
#### Post date: [September 8, 2021, 8:43pm UTC](https://discourse.paraview.org/t/python-plugin-failing-to-load-in-script-using-paraview-simple-loadstate-but-works-fine-in-gui/7960/1 "2021-09-08T20:43:00Z")

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I have created a Python plugin using `vtkmodules.util.vtkAlgorithm.VTKPythonAlgorithmBase`. This plugin works great in the GUI, but I am trying to use `paraview.simple.LoadState()` in a script so that I can parse my .pvsm state file into a .py state file. This operation fails, because one of the components of my plugin calls `vtk.vtkMultiProcessController.GetGlobalController().GetCommunicator()`. In the GUI, it returns a datatype `vtkMPICommunicator` for this call. But through `LoadState()`, it appears to return a datatype `vtkDummyCommunicator` and fails.

The relevant parts of the plugin that I am trying to use:

```auto
 29 import vtk
 30 _GC = vtk.vtkMultiProcessController.GetGlobalController()
 31 _RANK = _GC.GetLocalProcessId()
 32 _COMM = vtk.vtkMPI4PyCommunicator.ConvertToPython(_GC.GetCommunicator())
 33 print(type(_GC.GetCommunicator()))

```

Using the print statement on Line 33, I can tell that when it loads in the Paraview GUI, the datatype is `vtkMPICommunicator`.

Next I use that plugin filter in Paraview and save a .pvsm state file. After the .pvsm is saved, in my workflow I use another script to convert that .pvsm state file to .py. That script is reproduced below:

```auto
  4 import sys
  5 from paraview import simple as pvs
  6 from paraview import smstate
  7 
  8 pvsm_file = sys.argv[1]
  9 
 10 # Load pvsm state file
 11 pvs.LoadState(pvsm_file)

```

When I run that script, it crashes with the error trace in Python being:

```auto
  2 Failed to call `paraview.detail.pythonalgorithm.load_plugin`.^[[0m
  3 Traceback (most recent call last):
  4 File "/opt/Software/paraview/5.9.0_server/lib64/python3.7/site-packages/paraview/detail/pythonalgorithm.py", line 509, in load_plugin
  5 spec.loader.exec_module(module)
  6 File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  7 File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  8 File "path_to_plugin/plugin.py", line 30, in <module>
  9 _COMM = vtk.vtkMPI4PyCommunicator.ConvertToPython(_GC.GetCommunicator())
 10 TypeError: ConvertToPython argument 1: method requires a vtkMPICommunicator, a vtkDummyCommunicator was provided.

```

From that error trace, I am led to believe that something in `LoadState()` is forcing `_GC.GetCommunicator()` to output as datatype `vtkDummyCommunicator` instead of `vtkMPICommunicator`, which is what it does in the Paraview GUI.

Is there a solution to this? Is it a problem with `paraview.simple`, or is it a problem with my implementation?

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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: [September 9, 2021, 4:22pm UTC](https://discourse.paraview.org/t/python-plugin-failing-to-load-in-script-using-paraview-simple-loadstate-but-works-fine-in-gui/7960/2 "2021-09-09T16:22:59Z")

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Can you provide simple steps to reproduce with ParaView ?

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<div class="post-metadata">

### Author: ![csniker](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/c/c4cdca/32.png) [@csniker](https://discourse.paraview.org/u/csniker)
#### Post date: [September 9, 2021, 6:00pm UTC](https://discourse.paraview.org/t/python-plugin-failing-to-load-in-script-using-paraview-simple-loadstate-but-works-fine-in-gui/7960/3 "2021-09-09T18:00:07Z")

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@mwestphal  
Here is a step-by-step using simple inputs that I’ve confirmed reproduces what I’m seeing. I did not provide a source dataset, because I believe it will occur regardless of what source is being used. My datasets are not shareable.

1. Create a Python-based plugin that calls `vtk.vtkMultiProcessController.GetGlobalController().GetCommunicator()` within a `vtk.vtkMPI4PyCommunicator.ConvertToPython()` call. I have attached such a plugin. [discourse\_example\_plugin.py](https://discourse.paraview.org/uploads/short-url/pBjv8l5YfGEhdpoIKEHXF48ZbCA.py) (1.8 KB) [EDIT: fixed a typo in plugin]
2. Load that plugin into Paraview and make sure it is an auto-loaded plugin so that other scripts based on the Paraview Python APIs will recognize it (I am less confident on how this is done in a general sense. Within my company, this is handled by someone else).
3. Using some source (as I stated above, I believe it can be any source and still see the problem), apply the filter from the plugin in Step 1. Save this as a state file in .pvsm format.
4. Create a script that applies `paraview.simple.LoadState()` to the .pvsm file from Step 3. I have attached such a script. [discourse\_example\_script.py](https://discourse.paraview.org/uploads/short-url/A8GkxSvU7Pv1wfJrZTgb4cx0RkJ.py) (146 Bytes)
5. Run the script
6. If the same problem occurs which I am seeing, then this script will crash because the datatype of `vtk.vtkMultiProcessController.GetGlobalController().GetCommunicator()` is `vtkDummyCommunicator` when it should be `vtkMPICommunicator`

If that process doesn’t reproduce the same problem, then it could be particular to how I am using Paraview, in which case I would appreciate any help determining what is causing it.

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<div class="post-metadata">

### 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: [September 10, 2021, 9:37am UTC](https://discourse.paraview.org/t/python-plugin-failing-to-load-in-script-using-paraview-simple-loadstate-but-works-fine-in-gui/7960/4 "2021-09-10T09:37:45Z")

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FYI @utkarsh.ayachit (I did not test)

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### Author: ![utkarsh.ayachit](https://discourse.paraview.org/user_avatar/discourse.paraview.org/utkarsh.ayachit/32/39_2.png) [@utkarsh.ayachit](https://discourse.paraview.org/u/utkarsh.ayachit)
#### Post date: [September 11, 2021, 8:24pm UTC](https://discourse.paraview.org/t/python-plugin-failing-to-load-in-script-using-paraview-simple-loadstate-but-works-fine-in-gui/7960/5 "2021-09-11T20:24:02Z")

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Are you using `pvpython` to execute your script? Use `pvbatch` instead. `pvpython` does not initialize MPI by default since it’s not intended to use in distributed mode. Use `pvbatch` and you’ll always have an MPI controller available in an MPI-enabled build, irrespective of whether you’re actually running on more than 1 ranks.

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<div class="post-metadata">

### Author: ![csniker](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/c/c4cdca/32.png) [@csniker](https://discourse.paraview.org/u/csniker)
#### Post date: [September 13, 2021, 12:37pm UTC](https://discourse.paraview.org/t/python-plugin-failing-to-load-in-script-using-paraview-simple-loadstate-but-works-fine-in-gui/7960/6 "2021-09-13T12:37:14Z")

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@utkarsh.ayachit  
That worked! I wasn’t aware you could run the same tool in `pvpython` or `pvbatch`, so that’s a good lesson to know. I was just executing it on the command line as `python <script_name>`, and that must default to `pvpython`.

Thanks for your help!