Drawing polyline with user input points using PyQGIS

Question

I have an empty layer in QGIS in that I just want to draw a polyline by selecting points on layer using Python.

For example, if I select a start point and endpoint on a layer, I want to draw a line connecting to those points using Python code. I have gone through all related references but I didn't get it.

What I have tried is:

from qgis.gui import QgsMapToolEmitPoint
def display_point(point, mouse_button):
 coords = "Map Coordinates: {:.4f}, {:.4f}".format(point.x(), point.y())
 print coords
 
 layer = iface.activeLayer()
 feats = [ feat for feat in layer.getFeatures() ]
 geo_pt = QgsGeometry.fromPoint(QgsPoint(point.x(), point.y()))
 id = -1
 for feat in feats:
 if geo_pt.within(feat.geometry()):
 id = feat.id()
 break
 if id != -1:
 print feats[id].attribute('name')
 else:
 print "no feature selected"
canvas = iface.mapCanvas()
pointTool = QgsMapToolEmitPoint(canvas)
pointTool.canvasClicked.connect(display_point)
canvas.setMapTool(pointTool)

Answer 1

You could try to identify the selected features of the source layer with

sourceLayer.getSelectedFeatures()

and then create a line geometry from the list of points:

line = QgsGeometry.fromPolyline(list_of_points)

• Virat ABD: I got this error : AttributeError: 'QgsVectorLayer' object has no attribute 'getSelectedFeatures'
• Kadir Şahbaz: @ViratABD You probably use QGIS 2.x. getSelectedFeatures method is not defined in QGIS 2.x API. Use selectedFeaturesIterator for the same purpose.