Changing Symbology Value Field for FC in TOC using Python

Question

Hi there I've spent quite a while searching online and ArcGIS/ArcPy Help for a solution with no success, so I wonder if someone could think of a way around this issue: I would like to change the symbology Value Field of a Feature Class within an MXD. I need first to set the symbology of the FC to "Match to symbols in a style" using a Value Field and then use Python to change the Value Field keeping the same symbology style. I know that ArcGIS does not support "Match to symbols in a style" symbology Type but I wonder if there is away around this. It would be something like the script below but replacing the symbology Type with "something else". Hope I explained the issue clearly. Many thanks. import arcpy mxd = arcpy.mapping.MapDocument("CURRENT") lyrlist = arcpy.mapping.ListLayers(mxd) for lyr in lyrlist: if lyr.symbologyType == "UNIQUE_VALUES": lyr.symbology.valueField = "DESCRIPTION" lyr.symbology.addAllValues() arcpy.RefreshActiveView() arcpy.RefreshTOC() del mxd ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

anTonialcaraz · Answer

Hi again, Thanks to everyone that have had a look into this. I guess it is a tricky one. Just to add on my question/query: I have a macro written in VB by someone at the company quite a while ago that does what I intend to do (improve) in Python. I have no knowledge of VB so not really sure how to translate this into Python. I assume that if this can be done in VB it should also by possible in Python? Please see the VB code below and if you can help with this it would be greatly appreciated. Const STYLE_FIELD = "CSID" Const LABEL_FIELD = "Description" ' -------------------------------------------- Public Sub LabelStylesFromAnotherField() Dim pMxDoc As IMxDocument Dim pGeoFtrLyr As IGeoFeatureLayer Dim pLegInfo As ILegendInfo Dim pLegGrp As ILegendGroup Dim pLegCls As ILegendClass Dim f As Long Set pMxDoc = ThisDocument Set pGeoFtrLyr = pMxDoc.FocusMap.Layer(0) Set pLegInfo = pGeoFtrLyr.Renderer Set pLegGrp = pLegInfo.LegendGroup(0) For f = 0 To pLegGrp.ClassCount - 1 Set pLegCls = pLegGrp.Class(f) pLegCls.Label = GetStyleLabel(pLegCls.Label, STYLE_FIELD, LABEL_FIELD, pGeoFtrLyr) Next f pMxDoc.UpdateContents MsgBox "Updated Symbol Labels", vbInformation, "" End Sub Private Function GetStyleLabel(sStyle As String, sStyleField As String, sLabelField As String, pGeoFtrLyr As IGeoFeatureLayer) As String Dim pFtrCls As IFeatureClass Dim lStyFldIdx As Long Dim lLblFldIdx As Long Dim lID As Long Dim pQryFltr As IQueryFilter Set pFtrCls = pGeoFtrLyr.DisplayFeatureClass lStyFldIdx = pFtrCls.FindField(sStyleField) lLblFldIdx = pFtrCls.FindField(sLabelField) If lStyFldIdx = -1 Or lLblFldIdx = -1 Then GetStyleLabel = sStyle Exit Function End If Set pQryFltr = New QueryFilter pQryFltr.WhereClause = sStyleField + " = '" + sStyle + "'" lID = pFtrCls.Select(pQryFltr, esriSelectionTypeIDSet, esriSelectionOptionOnlyOne, Nothing).IDs.Next If lID = -1 Then GetStyleLabel = sStyle Exit Function End If GetStyleLabel = CStr(pFtrCls.GetFeature(lID).Value(lLblFldIdx)) End Function‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍