How to select all values by default in arcgis tool's multivalue parameter using python?

Question

I am using ArcGIS 10.2 and have three parameters, Feature class, field and a multivalue parameter respectively in ArcGIS tool. I populate multivalue parameter with unique values of feature class on selection of feature class and field. Here is the code snippet:

def updateParameters(self):

    if self.params[0].value and self.params[1].value:
        fc = str(self.params[0].value)
        col = str(self.params[1].value)
        self.params[2].filter.list = sorted(
                                         set(
                                             row[0] for row in arcpy.da.SearchCursor(fc, [col]) if row[0]
                                            )
                                           )

By default, none of the value is checked in the tool.

How can I check all values of multivalue parameter through ToolValidation class using python 2.7?

Answer 1

You can set the value of the parameter to the values you want to be checked, at least when using a Python Toolbox. The same should be true for your case.

For example:

def getParameterInfo(self):
    p = arcpy.Parameter()
    p.datatype = 'String'
    p.multiValue = True
    p.name = 'test'
    p.displayName = 'Test'
    p.parameterType = 'Required'
    p.direction = 'Input'
    p.filter.list = ['One','Two','Three','Four']
    return [p]

def updateParameters(self, parameters):
    parameters[0].value = ['Two','Four']        
    return

edit

For your code example this would look like:

def updateParameters(self):
    if self.params[0].value and self.params[1].value:
        fc = str(self.params[0].value)
        col = str(self.params[1].value)
        vals = sorted(set(row[0] for row in arcpy.da.SearchCursor(fc,[col]) if row))
        self.params[2].filter.list = vals
        self.params[2].value = vals