[QGIS-Developer] set data defined override expression with python?

[Raymond Nijssen]

Thank you Nyall! Does exactly what I need. Will add it to the python 
cookbook.

Raymond



On 22-08-18 00:10, Nyall Dawson wrote:
> On Wed, 22 Aug 2018 at 01:41, Raymond Nijssen <r.nijssen at terglobo.nl> wrote:
>>
>> Hi devs!
>>
>> I'd like my python plugin to set an expression for overriding a property
>> and I have no clue how to do so. I expect there must be some generic way
>> to set expressions.
>>
>> Specifically, I want to set the expression for the "Image source" of a
>> QgsLayoutItemPicture to:
>>
>> '/path/to/pictures/' || attribute(@atlas_feature, 'ID') || '.svg'
>>
> 
> Try
> 
>      property = QgsProperty.fromExpression( "'/path/to/pictures/' ||
> attribute(@atlas_feature, 'ID') || '.svg'")
>      item.dataDefinedProperties().setProperty(QgsLayoutObject.PictureSource,
> property)
> 
> Nyall
>