gistfile1.py

def mapselection(self):
    def add_city(feature):
		"""
		Add a city to the output list
		"""
        nearCity = feature['name']
        state = feature['state']
        state_and_cities = "{},{}".format(nearCity, state)
        lsNearCities.append(state_and_cities)

    filePath = self.dlg.fileNameEdit.text()
    if not filePath:
        QMessageBox.warning(self.dlg, "File Name","Give it a file name and try again")        
        return

    lsNearCities = []
   
    layer = QgsMapLayerRegistry.instance().mapLayersByName('us_cities')[0]
    selfeature = layer.selectedFeatures() 

    distance = self.dlg.DistancelineEdit.text()
    dist = float(distance) * (1609.344)

    if distance and dist != 0:
	    for feature in selfeature:
			mbuf = feature.geometry().buffer(dist, 2)
			iterFeat = layer.getFeatures()
			for f in iterFeat:
				geom2 = f.geometry()
				if geom2.within(mbuf):
					add_city(f)
    else:
            for feature in selfeature:
				add_city(feature)