Getting coordinates of point on mouse click using PyQGIS

Question

I want to get x/y coordinates of a point on mouse click for a point and need to use those coordinates to evaluate other values as per other modules already define.

How can I get x/y coordinates on mouse click in QGIS and print those in PyQGIS?

Answer 1

You need QgsMapToolEmitPoint class to do that. Following code works well for that purpose:

from qgis.gui import QgsMapToolEmitPoint

def display_point( pointTool ): 

    print '({:.4f}, {:.4f})'.format(pointTool[0], pointTool[1])

# a reference to our map canvas 
canvas = iface.mapCanvas() 

# this QGIS tool emits as QgsPoint after each click on the map canvas
pointTool = QgsMapToolEmitPoint(canvas)

pointTool.canvasClicked.connect( display_point )

canvas.setMapTool( pointTool )

However, if you prefer a class, following code can also be used:

from qgis.gui import QgsMapToolEmitPoint

class PrintClickedPoint(QgsMapToolEmitPoint):
    def __init__(self, canvas):
        self.canvas = canvas
        QgsMapToolEmitPoint.__init__(self, self.canvas)

    def canvasPressEvent( self, e ):
        point = self.toMapCoordinates(self.canvas.mouseLastXY())
        print '({:.4f}, {:.4f})'.format(point[0], point[1])

canvas_clicked = PrintClickedPoint( iface.mapCanvas() )
iface.mapCanvas().setMapTool( canvas_clicked )