CalculateField based on attribute in another layer

ZdeněkSoldán

Hello

I have list of layers from mxd save in a variable lyrs. I want to copy every layer to file gdb so I use for loop.  I need to preserve original OBJECTID in the new layers so I add a new field originOBJID into new layers. Is there any option/expression how to calculate field in new layer based on attribute OBJECTID from original layer (lyr in the for loop)??

mxd=arcpy.mapping.MapDocument("path")

lyrs=arcpy.mapping.ListLayers(mxd)

for lyr in lyrs:

    layr=arcpy.FeatureClassToFeatureClass_conversion(lyr,in_gdb,lyr.name)

    arcpy.AddField_management(layr,"originOBJID","LONG")

    arcpy.CalculateField_management(layr,"originOBJID","???")

Thanks a lot for help!

XanderBakker

To explain a bit how you could do this see the code below:

• On line 8 and 9 you should specify the paths to the existing input and non-existing output featureclasses (see examples on lines 6 and 7
• The code will generate a dictionary of the unique field INVCIS versus the original OBJECTID. See lines 15 - 17
• Next the featureclass is converted to the output featureclass on line 21
• On line 24 the additional field is added
• Lines 27 - 36 update the output featureclass and write the original OBJECTID to the field called originOBJID

def main():
    import arcpy
    import os

    # paths to input and output featureclasses
    # Database Connections\Desarrollo 10.1.sde\EPMGIS.DEPTO_TRANSPORTE\EPMGIS.DEPTO_Lyr_Via_Vehi
    # \Xander\GeoNet\3Dpoints_3Dlines\gdb\test.gdb\polylineZ
    fc_in = r''
    fc_out = r''

    fld_OIDout = 'originOBJID'
    fld_id = 'INVCIS'

    # generate dictionary (LUT)
    fld_OIDin = arcpy.Describe(fc_in).OIDFieldName
    flds = (fld_id, fld_OIDin)
    dct = {r[0]:r[1] for r in arcpy.da.SearchCursor(fc_in, (flds))}

    # transfer the data
    ws, fc_name = os.path.split(fc_out)
    arcpy.FeatureClassToFeatureClass_conversion(fc_in, ws, fc_name)

    # Add the additional field
    arcpy.AddField_management(fc_out, fld_OIDout, "LONG")

    # Update the unformation
    flds = (fld_id, fld_OIDout)
    with arcpy.da.UpdateCursor(fc_out, (flds)) as curs:
        for row in curs:
            uid = row[0]
            if uid in dct:
                row[1] = dct[uid]
            else:
                # this should not happen
                row[1] = -1
            curs.updateRow(row)

if __name__ == '__main__':
    main()

Question: if you have a unique field to start with, why would you want to hold a reference to the original OBJECTID?