Saturday, 26 September 2015

qgis - How to "Merge Selected Features" with python?


I have been looking for the answer to this question for some time now, but can't seem to find it! My problem is straight forward: I have one layer It contains lots of features (only polygons), say countrys I want to merge some features together. Using python.


I know that I can select features with the mouse and hit the "Merge selected features"-button, but that is to slow. I can use python to select the features that i want, but how can i merge the selected features from python? (the features don't have a "common field" or something like that, what features are to be merged will be decided by in-data)


Help is greatly appreciated!



Answer



You can use QgsGeometry.combine( QgsGeometry ) for that.


Just loop over all your features and call


geom = geom.combine( currentFeature.geometry() )

with geom being a QgsGeometry



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