I have converted a model to python in ArcGIS 10.3, and have found that the tool outputs a full and very very long field mapping. Is there a way to shorten this somehow? While I want all field names/types/lengths to stay the same, I don't necessarily want all fields to be output.

arcpy.TableToTable_conversion(SourceTable, TargetDB, "xxOutputTable", "", "RecordID \"RecordID\" true false false 8 Double 0 19 ,First,#,Database Connections\\\\GISDatabase.sde\\GISDatabase.dbo.v_InputTable,RecordID,-1,-1;Descript \"Descript\" true true false 65 Text 0 0 ,First,#,Database Connections\\\\GISDatabase.sde\\GISDatabase.dbo.v_InputTable,Descript,-1,-1;Status \"Status\" true true false 30 Text 0 0 ,First,#,Database Connections\\\\GISDatabase.sde\\GISDatabase.dbo.v_InputTable,Status,-1,-1;RecordName \"RecordName\" true true false 50 Text 0 0 ,First,#,Database Connections\\\\GISDatabase.sde\\GISDatabase.dbo.v_InputTable,RecordName,-1,-1;Owner \"Owner\" true true false 2000 Text 0 0 ,First,#,Database Connections\\\\GISDatabase.sde\\GISDatabase.dbo.v_InputTable,Owner,-1,-1;", "")

While the python works fine with it all there, I would like to be able to make it as simple as possible to modify if/when required, and I do find the long field mapping quite hard to read when scrolling through it across the screen.

Is there a way to simplify this expression?

  • 3
    Yes, you can create a FieldMappings object and add FieldMap objects to it. It's not the most intuitive process, but once you wrap your head around it it's quite useful. desktop.arcgis.com/en/desktop/latest/analyze/arcpy-classes/… – Emil Brundage Jan 7 '16 at 2:42
  • 1
    Or omit it entirely and suffer the consequences. If all you're after is a collection of geometries, with no regard to attribution (like building a mask for example), then you need not supply any field mappings. Every time I've used TableToTable or CopyFeatures without field mapping it works just fine; the Field Mappings object gives you a chance to change the field names on the way out. – Michael Stimson Jan 7 '16 at 4:09
  • @EmilBrundage - I've had a quick look at your link and think this might be on the right track if I can get my head around it. I'll have to have another in-depth read. – Midavalo Jan 7 '16 at 22:00
  • 1
    @MichaelMiles-Stimson - I've just tried this, leaving the field mapping blank and it's output all fields as-is. This would work I think as I can then use a Delete Fields to easily remove the fields I don't want, rather than trying to exclude them via the field mapping. – Midavalo Jan 7 '16 at 22:01
  • 1
    That works too. If you only have a few fields it could be possible to create an empty table, add the fields you want and use append. I have used that approach for feature classes with dozens of fields, of which I only want one or two, and a simplified field map or NO_TEST if the field names/types aren't being modified. – Michael Stimson Jan 8 '16 at 0:16

Using http://desktop.arcgis.com/en/desktop/latest/analyze/arcpy-classes/fieldmappings.htm as a guide, the following python works and makes adding/removing/modifying fields a lot easier than within with arcpy tool

import arcpy

def generateFieldMapping(fms, fieldName, fieldType, fieldLength, fieldPrecision, fieldScale, fieldAlias):
    # Create the FieldMap object
    fm = arcpy.FieldMap()
    fm.addInputField(SourceTable, fieldName)
    fm_field = fm.outputField

    # Set the different properties of the field
    fm_field.name = fieldName
    fm_field.aliasName = fieldAlias
    fm_field.type = fieldType
    if fieldType == "Text":
        fm_field.length = fieldLength
    if fieldType == "Integer" or fieldType == "Double":
        fm_field.precision = fieldPrecision
    if fieldType == "Double":
        fm_field.scale = fieldScale

    fm.outputField = fm_field

    # Add FieldMap to the FieldMappings object

    return fms

SourceDB = "Database Connections\\GISDatabase.sde"
TargetDB = "Database Connections\\GISDatabase.sde"

# Local variables:
SourceTable = SourceDB + "\\GISDatabase.dbo.v_InputTable"

fields = [
          # [Field Name, Field type, Length, Precision, Scale, Field Alias]

# Create the FieldMappings objects
fms = arcpy.FieldMappings()

for field in fields:
    generateFieldMapping(fms, field[0], field[1], field[2], field[3], field[4], field[5])

arcpy.TableToTable_conversion(SourceTable, TargetDB, "xxOutputTable", "", fms, "")

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