Arcpy: allow user input for predefined filter list of strings

Question

I've created a small toolbox where I use a GPString input with a filter list:

param1 = arcpy.Parameter(
    displayName="OSM tag value",
    name="in_key",
    datatype="GPString",
    parameterType="Required",
    direction="Input",
    multiValue=True
)
param1.filter.list = self.getConfig("tags")

The function getConfig reads a JSON and fills the values of the String input. Yet I want to enable the user to use an own string for the input at param1.

Is there any chance to do this with the given approach or do I need to create a second input for a user defined GPString?

Here is the issue on GitHub.

Answer 1

I would use GPValueTable instead of GPString to have plus button for adding user entries but this makes things a bit tricky since you need to set columns and work out filter updating mechanism. I ran a small test and I think rough workaround below might be of help.

After setting datatype="GPValueTable" you need these lines below

param1.columns = [['String', 'Desired Tags']]
param1.filters[0].type = 'ValueList'
# These are optional default values if needs be. If not just comment out the line below
param1.values = [['A place'], ['Or Not']]
param1.filters[0].list = self.getConfig("tags")

and you need to setup updateParameters as follows to add new user entries to filter list. You can even update your config file here or around execute:

def updateParameters(self, parameters):
    if parameters[1].altered:
        new_values = [i[0] for i in parameters[1].values if i[0] not in parameters[1].filters[0].list]
        parameters[1].filters[0].list += new_values