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I've got a Python script that "cleans up" a feature class by renaming fields to something more legible -- add a new field (e.g. "DistrictName"), copy data from old field (e.g. "DISTNAM") to new field, and delete the old field. This is done for a lot of fields, so I built functions:

def delete_field(tbl, fieldName):
    arcpy.DeleteField_management(tbl, fieldName)
def replace_field(tbl, newFieldName, oldFieldName, dataType):
    arcpy.AddField_management(tbl, newFieldName, dataType)
    with arcpy.da.UpdateCursor(tbl, [newFieldName, oldFieldName]) as cursor:
        for row in cursor:
            row[0] = row[1]
            cursor.updateRow(row)
    delete_field(tbl, oldFieldName)

But there's a subsequent step in the Python script that is exporting this feature class to an Excel spreadsheet, and part of the process builds a list of the fields to be used to create a header row of column names.

data_description = arcpy.Describe(dataset_name)
fieldnames = [f.name for f in data_description.fields if f.type not in ["Geometry", "Raster", "Blob"]]

When I look at the resulting feature class in ArcMap, all the old field names have been deleted, which is exactly what I would expect. When Python does that Describe step, it sees both the new AND the old field names -- but it breaks when attempting to copy an old field, since the data does not actually exist.

What step can I add between deleting and listing to "update" the feature class fields so it only lists the existing fields, and not any fields which were recently deleted?

EDIT: I pulled the Describe portion out of its function and put it directly after the sequence of replace_field operations. Also tried using arcpy.ListFields instead of the Describe method.

replace_field(tableName, "District_Name", "DISTRICTNAME", "TEXT")
replace_field(tableName, "District_Number", "DISTRICT", "LONG")
replace_field(tableName, "LocalOffice_Name", "LOCALOFFICENAME", "TEXT")
replace_field(tableName, "Substation_Number", "SUBSTATIONID", "LONG")
replace_field(tableName, "FeederID", "CIRCUITID", "LONG")
replace_field(tableName, "OH_SinglePhase_CircuitMiles", "OH_SINGLEPHASE", "DOUBLE")
replace_field(tableName, "OH_TwoPhase_CircuitMiles", "OH_TWOPHASE", "DOUBLE")
replace_field(tableName, "OH_ThreePhase_CircuitMiles", "OH_THREEPHASE", "DOUBLE")
replace_field(tableName, "OH_Total_CircuitMiles", "OH_TOTALCIR", "DOUBLE")
replace_field(tableName, "UG_SinglePhase_CircuitMiles", "UG_SINGLEPHASE", "DOUBLE")
replace_field(tableName, "UG_TwoPhase_CircuitMiles", "UG_TWOPHASE", "DOUBLE")
replace_field(tableName, "UG_ThreePhase_CircuitMiles", "UG_THREEPHASE", "DOUBLE")
replace_field(tableName, "UG_Total_CircuitMiles", "UG_TOTALCIR", "DOUBLE")

data_description = arcpy.Describe(tableName)
fieldnames = [f.name for f in data_description.fields if f.type not in ["Geometry", "Raster", "Blob"]]
print fieldnames

apyListFields = arcpy.ListFields(tableName)
print apyListFields

The resulting list of fields from both Describe and ListFields is the same -- and all the field names in caps (e.g. DISTRICTNAME) are deleted, but still showing up as field names.

[u'OBJECTID', u'District_Name', u'District_Number', u'LocalOffice_Name', u'Substation_Number', u'FeederID', u'OH_SinglePhase_CircuitMiles', u'OH_TwoPhase_CircuitMiles', u'OH_ThreePhase_CircuitMiles', u'OH_Total_CircuitMiles', u'UG_SinglePhase_CircuitMiles', u'UG_TwoPhase_CircuitMiles', u'UG_ThreePhase_CircuitMiles', u'UG_Total_CircuitMiles', u'UG_TOTALCIR', u'UG_THREEPHASE', u'UG_TWOPHASE', u'UG_SINGLEPHASE', u'OH_TOTALCIR', u'OH_THREEPHASE', u'OH_TWOPHASE', u'OH_SINGLEPHASE', u'CIRCUITID', u'SUBSTATIONID', u'LOCALOFFICENAME', u'DISTRICT', u'DISTRICTNAME']

[u'OBJECTID', u'District_Name', u'District_Number', u'LocalOffice_Name', u'Substation_Number', u'FeederID', u'OH_SinglePhase_CircuitMiles', u'OH_TwoPhase_CircuitMiles', u'OH_ThreePhase_CircuitMiles', u'OH_Total_CircuitMiles', u'UG_SinglePhase_CircuitMiles', u'UG_TwoPhase_CircuitMiles', u'UG_ThreePhase_CircuitMiles', u'UG_Total_CircuitMiles', u'UG_TOTALCIR', u'UG_THREEPHASE', u'UG_TWOPHASE', u'UG_SINGLEPHASE', u'OH_TOTALCIR', u'OH_THREEPHASE', u'OH_TWOPHASE', u'OH_SINGLEPHASE', u'CIRCUITID', u'SUBSTATIONID', u'LOCALOFFICENAME', u'DISTRICT', u'DISTRICTNAME']

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    Hey Erica - This is a guess, but perhaps something adverse and schema-lock related is happening between the closing of your with statement's frame, and the call to delete_field() immediately after it. Have you tried issuing the call to delete_field() outside of the replace_field() definition in this case? Otherwise, the code reads fine in my opinion, there is no obvious reason why it should not work as-is; in other words, something is happening that is not immediately the script's fault.
    – Jim
    Aug 10, 2016 at 16:59
  • @Jim It's likely some sort of very weird lock. I tried calling delete_field() without involving the replace_field() function, and ArcPy still sees the "deleted" field...
    – Erica
    Aug 10, 2016 at 18:51
  • 1
    That is... such odd behavior for ArcPy and probably outright frustrating for the user. I hope a solution appears soon.
    – Jim
    Aug 10, 2016 at 18:55
  • Yes, it's within another function to which you pass a feature class as dataset_name. It would also be called tbl except I didn't write it, it's from somebody else's module.
    – Erica
    Aug 10, 2016 at 21:19
  • So one doesn't refer to an in-memory copy, a layer, or anything else? They both refer to the same feature class path/name?
    – Tom
    Aug 10, 2016 at 21:24

1 Answer 1

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As a workaround, copying the "cleaned" feature class to a new feature class before attempting to list fields avoids the issue.

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