Adding a field to a vector layer
This recipe demonstrates adding a new field to a layer. Each field represents a new column in a data set for which each feature has a new attribute. When you add a new attribute, the attribute value for all existing features are set to NULL for that field index.
Getting ready
We will use the New York City museums shapefile used in other recipes, which you can download as a ZIP file here:
https://github.com/GeospatialPython/Learn/raw/master/NYC_MUSEUMS_GEO.zip
Extract this shapefile to /qgis_data/nyc.
How to do it...
All data management for a layer is handled through the layer's data provider, and fields are no different. We will load the layer, access the data provider, define the new field, and finalize the change:
Start QGIS.
From the Plugins menu, select Python Console.
First, we must import the Qt library data types that PyQGIS uses to specify layer field data types:
from PyQt4.QtCore import QVariant
Next, load and validate the layer:
vectorLyr...
