How to select the buffer region in map canvas in my plugin using python

I am developing a plugin which finds buffer by getting state name, city name and distance given by the user. The plugin works fine and writes the cities that matches the distance in a CSV file. What i want is the buffer region should get selected in the map canvas. How it can be done. I had attached my code below.

def calcDistance(self):
    lsNearCities = []

    filePath = self.dlg.fileNameEdit.text()

    if len(str(filePath)) ==0:
        QMessageBox.warning(self.dlg, "File Name","Give it a file name and try again")        
        return

    if self.dlg.DistancelineEdit.text():
        dist = float(self.dlg.DistancelineEdit.text())/(0.000621371)
    else:
        dist = 0

    centerCity = self.dlg.Citycombo.currentText()

    if dist and centerCity:
        #QMessageBox.information(self.dlg, "info", "both True")
        st = '"name" = \'' + centerCity + '\''
        exp = QgsExpression(st)
    else:
        QMessageBox.warning(self.dlg, "Enter the distance","Enter the distance and try again.")        
        return          #terminate the function

    layer = self.iface.activeLayer() 
    it = layer.getFeatures(QgsFeatureRequest(exp))
    feature = it.next()
    mbuf = feature.geometry().buffer(dist, 2)       

    iterFeat = layer.getFeatures()

    for f in iterFeat:
        geom2 = f.geometry()
        valTest = QgsGeometry.within(geom2, mbuf)

    if valTest:
            idx = layer.fieldNameIndex('name')  #name of the attribute column with the cities in it
            idx1 = layer.fieldNameIndex('state')
            nearCity = f.attributes()[idx]
            state = f.attributes()[idx1]
            state_and_cities = nearCity +","+ str(state)
            lsNearCities.append(state_and_cities) 
    #call the function to write them into a file
    self.writeToFile(lsNearCities, filePath)