line - Selecting features within certain buffer distance of selected feature using PyQGIS?

I have a shapefile of thousands of polylines. I have select one feature, I want to select all other features that is within say 100m of the selected feature.

How do I achieve it by pyqgis?

Answer

If you want to select all features that are within 100 m of the selected "buffer" feature you can use next code:

layer = iface.activeLayer()

feats = [ feat for feat in layer.getFeatures() ]

#selected feature fid = 0
geom_buffer = feats[0].geometry().buffer(100, -1)

#erasing selected feature in original list
del feats[0]


new_feats = [feat for feat in feats
             if feat.geometry().intersects(geom_buffer) ]

epsg = layer.crs().postgisSrid()

uri = "LineString?crs=epsg:" + str(epsg) + "&field=id:integer""&index=yes"

mem_layer = QgsVectorLayer(uri,
                           'line',

                           'memory')

prov = mem_layer.dataProvider()

for i, feat in enumerate(new_feats):
    feat.setAttributes([i])

prov.addFeatures(new_feats)

QgsMapLayerRegistry.instance().addMapLayer(mem_layer)

It produces a memory layer with features that match this condition.

I tried out above code with next line layer; where selected feature (id=0) was previously visualized as buffer by using its WKT format into QuickWKT plugin of QGIS.

After running the code, memory layer (red layer in next image) was obtained as expected: