add section on python in qgis (#244)

Author: pvgenuchten

workshop/jupyter/content/notebooks/04-vector-data.ipynb

@@ -1756,6 +1756,31 @@
     "```"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Python in QGIS \n",
+    "\n",
+    "QGIS uses Python much like standalone geospatial libraries, but instead of opening files manually, you usually\n",
+    "interact with layers already loaded in the QGIS project. Geometry operations resemble those in Shapely, though they\n", 
+    "use the `QgsGeometry` API rather than Shapely's methods. Unlike standalone scripts, the QGIS Python console provides\n",
+    "direct access to the current map, layers, and interface through objects such as `iface` and `QgsProject.instance()`.\n",
+    "Many workflows combine both worlds, using PyQGIS for project interaction and Shapely, RasterIO, NumPy, or Pandas for\n",
+    "specialized analysis.\n",
+    "\n",
+    "If you have QGIS installed, try below scripts in the `Python Console` (in the `Plugins` menu).\n",
+    "\n",
+    "```\n",
+    "layer = QgsProject.instance().mapLayersByName('roads')[0]\n",
+    "print(layer.name())\n",
+    "for feature in layer.getFeatures():\n",
+    "   print(feature.id())\n",
+    "   print(feature.get('name'))  # attribute field\n",
+    "   print(feature.geometry().asWkt()) # geometry\n",
+    "```\n"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},