# Python bindings for custom PV widgets
**URL:** https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921
**Category:** Development
**Tags:** python
**Created:** [November 6, 2019, 4:17pm UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921 "2019-11-06T16:17:33Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [November 6, 2019, 4:17pm UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/1 "2019-11-06T16:17:33Z")
Dear PV devs,
I hope you could assist with the following challenge:
We have conjured a small xml/C++ plugin with custom QT widgets and not all of them are represented in the XML file. Now we would like to manipulate the widget values via a python script, similar to how “trace” and “paraview.simple” would do it.
Could you give some directions on how such PV-friendly python bindings could be implemented?
My sincere gratitude,
Art
---
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [November 14, 2019, 12:08pm UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/2 "2019-11-14T12:08:20Z")
We have figured it out! The answer was right in front of us, i.e. Q\_PROPERTY.
Many thanks,
Art
---
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [January 9, 2020, 4:05pm UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/3 "2020-01-09T16:05:03Z")
Dear all,
Our success with Q\_PROPERTY was somewhat limited, hence I ask for assistance once again.
To recap, we have a C++ plugin with internal variables A, B, where A is a float and B is a string. We would like to set these variables within ParaView’s python console as
```
plugin.A = 2.5
plugin.B = "string"
```
Currently, the connection to python is done via this construct
```
Q_PROPERTY(QList Values READ GetValues WRITE SetValues)
```
which enables the above python calls. However, the Q\_PROPERTY approach turned out to have a notable flaw, namely **QList\** in C++ translates into python as **list of floats** _only_, although QVariance can contain numbers, strings and more.
Is there any other approach to connect C++ plugin to a python console in ParaView? Is the Q\_PROPERTY approach not meant to be used this way in the first place?
Any expertise on the matter is appreciated. Many thanks,
Art
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [January 9, 2020, 4:27pm UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/4 "2020-01-09T16:27:21Z")
Q\_PROPERTY is definitely meant to be used in a custom property widget.
See `Plugins/LagrangianParticleTracker/pqIntegrationModelSeedHelperWidget.h` for an example.
---
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [January 10, 2020, 9:14am UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/5 "2020-01-10T09:14:28Z")
Hello Mathieu,
Thank you for a prompt reply.
Our implementation is very similiar to your example. Specifically, here is our C++ part:
```
(plugin.h)
Q_PROPERTY(QList Values READ GetValues WRITE SetValues)
```
and
```
(plugin.cpp)
void plugin::SetValues(const QList& values)
{
if(values.count() == 0)
return;
std::cout << "values[0] = " << values[0].toString().toStdString() << std::endl;
std::cout << "values[1] = " << values[1].toString().toStdString() << std::endl;
}
```
When updated from a python console as `plugin.values = [1, 3.5]`, the (correct) output is
```
values[0] = 1
values[1] = 3.5
```
But this update `plugin.values = [1, 'a']` (with a char/string) raises an error:
```
../paraview/servermanager.py", line 820, in SetData
self.SMProperty.SetElement(idx, val)
TypeError: SetElement argument 2:
```
which, if I understand correctly is an index error. Yet, the number of elements in the array is the same. I can’t figure out what I’m doing wrong here.
Thanks a lot,
Art
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [January 10, 2020, 9:15am UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/6 "2020-01-10T09:15:20Z")
Are you using a StringVectorProperty in your XML file ?
---
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [January 10, 2020, 9:23am UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/7 "2020-01-10T09:23:59Z")
That is it!
It was a \, changing to \ removed the error.
Two more questions:
(1) Is there a way to have a mixture of doubles and strings?
(2) Can I have nested structures like lists inside lists?
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [January 10, 2020, 9:27am UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/8 "2020-01-10T09:27:04Z")
1. StringVectorProperty allows you to specify the element types, int double or string. Search for `element_types`
2. No, but you can have _sort of_ two dimensional vectors by using `number_elements_per_command`
---
### Author:  [@siver](https://discourse.paraview.org/u/siver)
#### Post date: [January 10, 2020, 9:31am UTC](https://discourse.paraview.org/t/python-bindings-for-custom-pv-widgets/2921/9 "2020-01-10T09:31:07Z")
I will look into `element_types`, thanks a lot.
I also saw in your example that you emulate nested structures by splitting strings via a separator `;`, we might try that as well.
Thanks a lot for all the help.
Best,
Art