{"id":6243,"date":"2018-09-05T04:30:37","date_gmt":"2018-09-05T02:30:37","guid":{"rendered":"http:\/\/www.sigterritoires.fr\/?p=6243"},"modified":"2018-10-17T12:04:15","modified_gmt":"2018-10-17T10:04:15","slug":"python-methods-for-qgis-how-to-examine-vector-data","status":"publish","type":"post","link":"https:\/\/www.sigterritoires.fr\/index.php\/en\/python-methods-for-qgis-how-to-examine-vector-data\/","title":{"rendered":"Python Methods for QGis: how to examine vector data"},"content":{"rendered":"\r\n\r\n\r\n

Once a layer is loaded, usually we want to access the data included in the layer, whether the geometries or the attributes. Now, we will discuss how to code in Python the access to these two types of data.<\/p>\r\n\r\n\r\n\r\n

How to access<\/strong> the<\/strong> geometry<\/strong> of<\/strong> a<\/strong> vector layer<\/strong><\/h2>\r\n\r\n\r\n\r\n

We will resume the loading of a shapefile<\/a> script previously created (load_vector.py)<\/p>\r\n\r\n\r\n\r\n

 <\/p>\r\n\r\n\r\n\r\n\r\n\r\n

\u00a0\u00bb \u00a0\u00a0 \u00a0\u00bb \u00a0 \u00bbYour description of the script goes here\u00ab \u00a0\u00a0 \u00a0\u00bb \u00a0 \u00ab\u00a0<\/p>\r\n\r\n\r\n\r\n

# Some commonly used imports<\/p>\r\n\r\n\r\n\r\n

from PyQt4.QtCore import *
from PyQt4.QtGui import *
from qgis.core import *
from qgis.gui import *<\/p>\r\n\r\n\r\n\r\n

def run_script ( iface ):
qfd = QFileDialog ()
title = ‘ Open a file ‘
path = \u00a0\u00bb \u00a0 C: \/ \u00a0 \u00a0\u00bb
f = QFileDialog.getOpenFileName ( qfd , title, path)
layer = QgsVectorLayer (f, \u00a0\u00bb \u00a0 Museums in New York City \u00a0 \u00bb,\u00ab \u00a0 ogr \u00a0 \u00ab\u00a0)
if not layer.isValid ():
print \u00ab \u00a0 loading error of% s layer \u00a0 \u00bb% Layer.name ()
QgsMapLayerRegistry.instance (). addMapLayers ([layer])<\/p>\r\n[\/stextbox]<\/figure>\r\n\r\n\r\n\r\n\r\n\r\n

Replace the last line<\/p>\r\n\r\n\r\n\r\n

QgsMapLayerRegistry.instance<\/em><\/strong> ().<\/em><\/strong> addMapLayers<\/em><\/strong> ([layer])<\/em><\/strong><\/p>\r\n\r\n\r\n\r\n

by\u00a0<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n