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I have a folder of shapefiles which I want to append to project geodatabase feature classes using ArcPy. So far, as I am testing with just a few shapefiles, the script works fine as long as all the fields match and there is no field mapping involved. However, I would like to include field mapping with the code, but being relatively new to Python and ArcPy, I am having trouble understanding the best way to do this.

I would like to match the following fields: "reference" (in shapefile) with "ID" (feature class in GDB) and "riskcategory" (in shapefile) with "risk" (feature class in GDB).

My current code is below:

import arcpy
import os

#Set up workspace
workspace_in = arcpy.GetParameterAsText(0)
workspace_out = arcpy.GetParameterAsText(1)
arcpy.env.workspace = workspace_in

#Set target datasets
targetPt = os.path.join(workspace_out, "tree_location_pt")
targetPly = os.path.join(workspace_out, "tree_location_ply")

#get a list of shapefiles
survey = arcpy.ListFeatureClasses()

#loop shapefiles in folder
for fc in survey:
    if fc == "export_Point.shp":
        arcpy.management.Append(fc, targetPt, "NO_TEST")
    elif fc == "export_Polygon.shp":
        arcpy.management.Append(fc, targetPly, "NO_TEST")
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  • 2
    Please Edit the Question to include one or more of the field_mapping parameters you have attempted and include any error(s). Commented Nov 2, 2023 at 19:00
  • I would like to rephrase - the code that I have now works without field mapping, how can I add a field map for the two fields described in the main question? Any parameters that I might have tried are examples of other people's codes or ESRI append tool examples online and having tested them without actually understanding what I was doing. Now I finally have a code that works without field mapping - I would like to know what I can add to the current code to make a field map work? Thank you. Commented Nov 2, 2023 at 19:32
  • Your code looks like ArcGIS for Desktop, in that case you can create a field map object resources.arcgis.com/en/help/main/10.2/index.html#//… if you know the from and to field names... beware of types though, mapping a text to date (for example) is likely to result in facepalms. You can get info on input fields using ListFields(YourFC,FieldName)[0].type ListFields resources.arcgis.com/en/help/main/10.2/index.html#//… field type resources.arcgis.com/en/help/main/10.2/index.html#//… Commented Nov 3, 2023 at 0:57

4 Answers 4

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I have struggled with the fieldmap object myself, but figured it out eventually. Here's how it works. This should work in both ArcGIS Desktop and ArcGIS Pro.

source = r"path-to-source-featureclass"
target = r"path-to-target-featureclass"

# Get field objects from target featureclass
fields = arcpy.ListFields(target)

# Create a new object that will hold the field mappings
mappings = arcpy.FieldMappings()

# repeat the following 4 lines for every field you want to map
fieldmap = arcpy.FieldMap()
fieldmap.addInputField(source, "field-in-source")
fieldmap.outputField = next(f for f in fields if f.name == "field-in-target")
mappings.addFieldMap(fieldmap)

arcpy.management.Append(source, target, 'NO_TEST', mappings)

Note that inputField can be specified as just the fieldname (a string value), but outputField must be a field object.

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  • I have tested this code exactly as you have specified with my own source/target names. The script runs with no errors, but field mapping does not get read. The data transfers with empty attributes. I have managed to create a field mapping object successfully according to Append Example 3 [pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/… but, can only make it work for one target (I have two targets, polygon and point feature classes) - the target I place first in the script gets read. Have not found a way to include field map objects for multiple targets. Commented Nov 3, 2023 at 10:22
  • You will probably need to generate separate mapping for each target, because the outputFields are specific to the target of the Append method Commented Nov 3, 2023 at 11:12
  • Another option is to run the tool from a toolbox first, and generate Python code from the tool's result window. That might give you some idea for your own script Commented Nov 3, 2023 at 11:15
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import arcpy
import os

#Set up workspace
workspace_in = arcpy.GetParameterAsText(0)
workspace_out = arcpy.GetParameterAsText(1)
arcpy.env.workspace = workspace_in

#Set target datasets
targetPt = os.path.join(workspace_out, "tree_location_pt")
targetPly = os.path.join(workspace_out, "tree_location_ply")

#get a list of shapefiles
survey = arcpy.ListFeatureClasses()

#loop shapefiles in folder
for fc in survey:
    if fc == "export_Point.shp":
        # arcpy.management.AddField(fc, "reference", "LONG",)  # 1. shp add field.
        # arcpy.management.AddField(fc, "riskcategory", "TEXT",field_length=50) 
        ## Field are added automatically when calulating field
        arcpy.management.CalculateField(fc, "reference", "!ID!")  # 2. calulate field.
        arcpy.management.CalculateField(fc, "riskcategory", "!risk!") 
        arcpy.management.Append(fc, targetPt, "NO_TEST")  # 3. append shp to fc.
    elif fc == "export_Polygon.shp":
        # Same as pt
        arcpy.management.Append(fc, targetPly, "NO_TEST")
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0

I have managed to find a solution to this now so wanted to share my solution in case anyone ever comes across a similar issue. Maybe this is not the most elegant solution and can be trimmed down but it works - something that I was never able to achieve with ModelBuilder due to differing geometry types.

I have created the field mapping objects and append tool for point and polygon classes inside functions to be able to set separate field mapping targets due to differing geometries - and then calling these functions in the end of the script.

import arcpy
import os


def append_pt(workspace_in, workspace_out):

    #Set up workspace
    workspace_in = arcpy.GetParameterAsText(0)
    workspace_out = arcpy.GetParameterAsText(1) 
    arcpy.env.workspace = workspace_in


    #Set target datasets
    targetPt = os.path.join(workspace_out, "tree_location_pt")

    #Set local variables
    schemaType = "NO_TEST"
    fieldMappings = ""
    subtype = ""

    #Get a list of shapefiles
    surveypt = arcpy.ListFeatureClasses()

    #Create FieldMappings object
    fieldMappings = arcpy.FieldMappings()

    # Add the target table to the point field mappings class to set the schema
    fieldMappings.addTable(targetPt)

    #Add input fields for  point "reference"
    fldMap = arcpy.FieldMap()
    fldMap.addInputField("export_Point.shp", "reference")

    #Set the name of new output field
    ID = fldMap.outputField
    ID.name = "ID"
    fldMap.outputField = ID

    #Add output field to field mapping object
    fieldMappings.addFieldMap(fldMap)

    #Add input fields for "riskcatego"
    fldMap = arcpy.FieldMap()
    fldMap.addInputField("export_Point.shp", "riskcatego")

    #Set the name of new output field
    risk = fldMap.outputField
    risk.name = "Risk"
    fldMap.outputField = risk

    #Add output field to field mapping object
    fieldMappings.addFieldMap(fldMap)

    #loop shapefiles in folder
    for fc in surveypt:
        arcpy.AddMessage(fc)
        if fc == "export_Point.shp":
            arcpy.management.Append(fc, targetPt , schemaType, fieldMappings, subtype)

#Repeat the function above but for polygon dataset parameters

#Call append function
append_pt("arcpy.GetParameterAsText(0)", "arcpy.GetParameterAsText(1)")
append_ply("arcpy.GetParameterAsText(0)", "arcpy.GetParameterAsText(1)")
arcpy.AddMessage("Append Complete")
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Maybe you should use the Add Relate (Data Management)https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/add-relate.htm?

Make Feature Layer (Data Management) https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/make-feature-layer.htm

arcpy.management.MakeFeatureLayer(shp, shp_layer)     
arcpy.management.AddRelate(shp_layer, "reference", fc, "ID", "Relate_A") # Relate_A in workspace, fc in gdb or shp in floder. 
arcpy.management.AddRelate(shp_layer, "riskcategory", fc, "risk", "Relate_B")

arcpy.management.MakeFeatureLayer("realPath_Relate_A", Relate_A_layer) 
arcpy.management.AddRelate(Relate_A_layer, "FID_SHP", "Relate_B", "FID_SHP", "RESULT")
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  • 1
    The Append is used for the purpose of uploading survey data collected in the field weekly into a project database, so would really need to go with that particular tool. I would have the option to just change my geodatabase fields to match the survey fields or vice versa, but would very much like to figure out the field_mappings (since I know it is possible) without having to change existing practices. Commented Nov 2, 2023 at 20:11

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