AttributeError: 'QgsVectorLayer' object has no attribute 'fieldNameIndex'

Question

When I try to calculate a new field with:

idx = layer.fieldNameIndex(attributeName)

I receive the following error:

AttributeError: 'QgsVectorLayer' object has no attribute 'fieldNameIndex'

What ́s the problem? I'm using QGIS 3.0.1 64x in Windows.

• Taras: Please, do not forget about "What should I do when someone answers my question?"

Answer 1

In PyQGIS 3

Use one of the following methods from the QgsFields class:

1. indexFromName()

   layer = iface.activeLayer()
   layer_fields = layer.fields()
   field_index = layer_fields.indexFromName("FIELD_NAME")
   

2. lookupField():

   layer = iface.activeLayer()
   layer_fields = layer.fields()
   field_index = layer_fields.lookupField("FIELD_NAME")
   

3. indexOf()

   layer = iface.activeLayer()
   layer_fields = layer.fields()
   field_index = layer_fields.indexOf("FIELD_NAME")
   

Answer 2

You need to access it via the fieldNameIndex() method of the QgsVectorDataProvider class:

layer = iface.activeLayer()
idx = layer.dataProvider().fieldNameIndex(attributeName)

• Marco: How do you do that in the Python console? I'm a noob.
• Joseph: @MarcoUscuchagua - Click on a layer and type layer = iface.activeLayer(). Then type idx = layer.dataProvider().fieldNameIndex("fieldName"). The self` parameter is mainly used for plugins.
• Marco: The error remains. I think it is a error of QGIS and not of my layer.
• Joseph: @MarcoUscuchagua - What error are you receiving? Is it the same error as in your question?
• Marco: I found the solution!! The problem was in the Quick Attribution plugin, its reinstallation solved the problem. Thanks @Joseph