How to make default field in Python Scripts for Processing Framework (QGIS)

Question

I am building a Python Scripts for Processing Framework

https://docs.qgis.org/2.14/en/docs/pyqgis_developer_cookbook/processing.html

I know how to make default value when the data type is number or boolean:

##Distance=number 50
##carry_test=boolean True

I also know how to make fields in the layer into a drop down table and let user choose from:

##input_layer=vector
##cal_field=field input_layer

Is there a way to populate a default field as well? Say the layer has the following fields:

fid, name, type, color

Normally everytime the user has to check the drop down to choose 'type'. So it is kind of trouble, is there a way to choose the 'type' everytime when the input_layer has the field 'type'?

• gisnside: Could you be more specific on what you need to populate ? You might need to ask for a new field name, then launch an update on your new field within the code like in here : gis.stackexchange.com/questions/236745/…
• benchenggis: I have edited my question

Answer 1

I don't think this is currently possible as at the moment, you can only specify:

##Field=[optional] field [number|string] Parentinput

where:

• Field - Name of the field parameter in the GUI.
• [optional] - Optional option to make it...optional.
• field - The parameter used to list the fields in the layer.
• [number|string] - Optional filter to only list numeric or string fields in the layer.
• Parentinput - The layer to read the fields from.

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In the more recent processing version, you will also be able to filter date fields but there doesn't to be a method (yet) to allow default values for fields. You can always ask this as a feature request though.