[QGIS-Developer] Custom python expression question

[Marco Grisolia]

Hi Andreas,
I don't know if it is the best way for doing it, but I generally add the
current feature and the current layer as input parameters of the custom
function:

def my_function(layer_name, curr_feat, feature, parent):

They are set as inputs in this way when calling the custom function:

my_function(@layer_name, $currentfeature)

Then, I can simply call the current layer and the current feature inside
the function in this way:

layer = QgsMapLayerRegistry.instance().mapLayersByName(layer_name)[0]

geom = curr_feat.geometry()

For a better understanding, you may also have a look to my recent answer on
this question on GIS Stack Exchange [0]:

[0]
https://gis.stackexchange.com/questions/235014/increasing-marker-size-based-on-number-of-points-at-same-location-in-qgis

I hope that helps.
Best regards,
Marco





2017-05-05 10:45 GMT+02:00 Neumann, Andreas <a.neumann at carto.net>:

> Hi,
>
> If one creates a custom python expression, one gets a reference to the
> "feature" and the "parent".
>
> Question: what is "parent" referring to? What object type is it?
>
> Is it somehow possible in the Python script to get a reference to the
> layer the feature is part of? Would there be some example Python code
> around that shows how one can get access to the layer the feature belongs
> to?
>
> Thank you for any hints,
>
> Andreas
>
>
> _______________________________________________
> QGIS-Developer mailing list
> QGIS-Developer at lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-developer/attachments/20170505/3e5af794/attachment.html>