Is there any example about how to create a virtual field and subsequently change the attribute of a non-virtual field without wiping out the virtual field? Both are required to be done in the Python Console.
QGIS – Creating Virtual Field in QGIS Python Console
pyqgisqgisqgis-python-consolevirtual-field
Related Solutions
After getting around cookbook, the best place to learn is referring the QGis API Documentation. In this case we are looking for zoom functions, which are related to map canvas. So check if QgsMapCanvas class contains something.
Zoom functions available in QGis are provided in QgsMapCanvas Class.
>>> canvas = qgis.utils.iface.mapCanvas()
>>> canvas.zoomIn()
>>> canvas.zoomOut()
>>> canvas.zoomToFullExtent()
Fisrt, your field needs to be quoted.
Now look this example, the first one is to add the sum of all the field in each row; the second one, is to sum by row in a specific field.
You have Integer or Real (decimal number) to set your field, depending on what you need to get.
Best Answer
When you have a variable
layerthat is a reference to a vector layer you needto specify the field definition
add the new field with an expression
You can now modify an attribute and when you query the layer next time the virtual field will be updated.