drop list from field to execute SQL request

Question

I'm trying to create a python script that allows a selection attribute based on the name of a field in the attribute table of a layer.

I would like to configure my script such a way that permits the user to select the SOURCE NAME from a drop-down list. Here's the code I have written:

import arcpy
arcpy.env.workspace = 'in_memory'
arcpy.env.overwriteOutput = True 
mxd = arcpy.mapping.MapDocument("CURRENT")
df = arcpy.mapping.ListDataFrames(mxd)[0]
PosteLayer=arcpy.GetParameterAsText(0)
field="NAME_SOURCE"
rows=arcpy.da.SearchCursor(PosteLayer,["NAME_SOURCE"])
list=[]
for row in rows:
   if str(row[O]) not in list:
       liste.append(row[0])
POSTES=liste
POSTES=arcpy.GetParameterAsText(1)

I'm using the Advanced Version Of Arcgis 10.2

Answer 1

First: you should make a toolbox with a script set the parameters the name "List of Source Name" the data type "string" the filter "value list as in picture:

Second: select Validation the edit button write under the (def updateParameters(self)) the following:

def updateParameters(self):

        #define the path of your feature class
        fc="D:/000/test.shp"
        #define the the name of the field
        col=  ("SOURCENAME")
        self.params[0].filter.list = [str(val) for val in  
                                        sorted(  
                                          set(  
                                            row.getValue(col)  
                                            for row in arcpy.SearchCursor(fc, None, None,col)))]  
        if self.params[0].value not in self.params[0].filter.list:  
          self.params[0].value = self.params[0].filter.list[0]
        return

Third: create a tool script and write the following:

import arcpy
mxd = arcpy.mapping.MapDocument("CURRENT")
currentlayer = arcpy.mapping.ListLayers(mxd, "*") [0]
inputLayer = arcpy.MakeFeatureLayer_management(currentlayer)  
TWN = arcpy.GetParameterAsText(0)
query  = "SOURCENAME = '" + TWN + "'"
arcpy.SelectLayerByAttribute_management(currentlayer, "NEW_SELECTION",  query )
count = arcpy.GetCount_management(currentlayer)
arcpy.AddMessage("thes selected are:  "+str(count))

or you can write in the validation script the following:

def updateParameters(self):
    #define the top layer in the mapview
    mxd = arcpy.mapping.MapDocument("CURRENT")
    fc = arcpy.mapping.ListLayers(mxd, "*") [0]

    #define the the name of the field
    col=  ("SOURCENAME")
    self.params[0].filter.list = [str(val) for val in  
                                    sorted(  
                                      set(  
                                        row.getValue(col)  
                                        for row in arcpy.SearchCursor(fc, None, None,col)))]  
    if self.params[0].value not in self.params[0].filter.list:  
      self.params[0].value = self.params[0].filter.list[0]
    return