21 Oct 2015

QGIS Processing Script for Quick Feature Selection and Zoom

Here's a little QGIS processsing script which might come in handy for you as well, if you've got to visually check many features and need to find/select/zoom them manually by attribute values. Using the attribute table's functions (find by expression, etc.) is rather cumbersome, if you have to iterate over loads of features for visual control - that's where the below script kicks in: You call the processing script from the processing toolbox panel (I like to have this one always visible) and just type in the feature's attribute value you're searching for, then, with one go, this feature is selected and zoomed. The zoom-value (2500) is hard coded into the script as well as the default layer (the one you're currently working with), for the sake of not having to put all of this manually each time (so you'll have to change this for your own purpose;).

from PyQt4.QtCore import *
from qgis.core import *
from qgis.utils import *

##[User scripts]=group
##Name_Layer=string 81127GST_V2
# Gst_Nr is the field in which we are searching
# 81127GST_V2 is the default layer for searching

canvas = iface.mapCanvas()

# First zoom to desired scale
canvas.zoomScale( 2500 )

allLayers = canvas.layers()
n = len(allLayers)
for i in range(0, n):
    if allLayers[i].name() == Name_Layer:
tarL = allLayers[i]

# Get a featureIterator from an expression
expr = QgsExpression( "\"GNR\"='" + Gst_Nr+ "'" )
it = tarL.getFeatures( QgsFeatureRequest( expr ) )

# Build a list of feature Ids from the result obtained above
ids = [j.id() for j in it]

# Select features with the ids
tarL.setSelectedFeatures( ids )

# Zoom to selected features
canvas.zoomToSelected( tarL )