topic How to copy some fields from one feature class to an existing fc in Python Questions

How to copy some fields from one feature class to an existing fc

DougWolfinger2 — Thu, 25 Apr 2019 16:16:22 GMT

I need to copy some fields from one shapefile to another existing one, preferably using Arcpy. Below is my code that checks for common fields between two shapefiles. Can I use this and add code to copy the fields that are not already in the destination shapefile from the original? What function will do that for me? I do not want data to transfer over--just the fields. Thank you!

>>>#FIELDS is the list of fields from the shapefile to copy from
#FIELDS2 is the list of fields already in the shapefile to copy to
fields = arcpy.ListFields("G:/Working Folder/Backup.gdb/PubData_RoadCenterlines")
... fields2 = arcpy.ListFields(r"G:\Data\External\Fairfield_County\Dupage_Centerlines_Web_Mercator_1984.shp")
... namelist = []
... namelist2 = []
... x = 0
... y = 0
... for field in fields:
... #populate NAMELIST[] with FIELDS
- namelist.append(field.name)
... #check the to shapefile for fields it already has and are common with the from shapefile
- for field2 in fields2:
... namelist2.append(field2.name)
... if namelist2 == namelist:
... print namelist + "is common between the two shapefiles"
... x+=1
... y+=1

Re: How to copy some fields from one feature class to an existing fc

leomonterol — Sun, 12 Dec 2021 05:24:27 GMT

Hi Doug

Try this:

shp01 = r'C:\tmp\New_Shapefile01.shp'
shp02 = r'C:\tmp\New_Shapefile02.shp'

fieldsShp01 = arcpy.ListFields(shp01)
fieldsShp02 = arcpy.ListFields(shp02)

newFields = []

for field01 in fieldsShp01:
	exists = False
	for field02 in fieldsShp02:
		if (field01.name == field02.name and field01.type == field02.type and field01.length == field02.length):
			exists = True
#			print("The {0} field with a type of {1} and a length of {2} exists in both shapefiles"
#				.format(field01.name, field01.type, field01.length))
	if (exists == False):
#		print("The {0} field with a type of {1} and a length of {2} exists only in shp 01"
#			.format(field01.name, field01.type, field01.length))
		newFields.append([field01.name, field01.type, field01.length])		

for field in newFields:	
	arcpy.AddField_management(shp02, field[0], field[1], "", "", field[2], "", "NON_NULLABLE","NON_REQUIRED","")
	print("The {0} field with a type of {1} and a length of {2} was added to shp 02"
		.format(field[0], field[1], field[2]))‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

For documentation on the Add Field tool you can navigate here.

Regards,

Leo

Re: How to copy some fields from one feature class to an existing fc

DougWolfinger2 — Fri, 26 Apr 2019 19:57:55 GMT

Hi Leo,

Thank you so much. I'll take a close look at this over the weekend. But for now it is throwing an exception at the AddField_management() line:

... for field in newFields:

... arcpy.AddField_management(shp02, field[0], field[1], "", "", field[2], "", "NON_NULLABLE","NON_REQUIRED","")

... print("The {0} field with a type of {1} and a length of {2} was added to shp 02"

... .format(field[0], field[1], field[2]))

...

So I removed field[0] and field[1], then got this error:

There are no field names that start with a number in the source layer. Like I said, I'll work with this later.

Thanks Again!

Doug

Re: How to copy some fields from one feature class to an existing fc

MicahBabinski — Fri, 26 Apr 2019 20:19:22 GMT

Hi Doug,

Try moving the print statement that you use right after the add field function up so that it prints what is supposed to be added. I think that will give you the info you need to solve the problem. Based on the error you received I believe that your script is trying to add a field with an invalid type to the target shapefile.

Micah

Re: How to copy some fields from one feature class to an existing fc

leomonterol — Mon, 29 Apr 2019 12:51:25 GMT

Hi Doug

Please try Micah's suggestion (place print statement before arcpy.AddField_management) to see the properties (name, type, length) of the field you're trying to add.

Regards,

Leo

Re: How to copy some fields from one feature class to an existing fc

DougWolfinger2 — Tue, 07 May 2019 19:57:45 GMT

I finally got a chance to get back into this and got it working. I moved the last print statement above the add field call :
... print("The {0} field with a type of {1} and a length of {2} was added to shp 02"
... .format(field[0], field[1], field[2]))
... arcpy.AddField_management(shp02, field[0], field[1], "", "", field[2], "", "NON_NULLABLE","NON_REQUIRED","")
...

..... and got this error message: ... for field in newFields:
The OBJECTID field with a type of OID and a length of 4 was added to shp 02
Runtime error Traceback (most recent call last): File "<string>", line 24, in <module> File "j:\apps\arcgis\desktop10.4\arcpy\arcpy\management.py", line 3149, in AddField raise e ExecuteError: ERROR 000800: The value is not a member of TEXT | FLOAT | DOUBLE | SHORT | LONG | DATE | BLOB | RASTER | GUID.

So I added a nested IF to bypass the adding of OBJECTID because it looked like it balked at adding it. I suppose this is because every shp has a field like that by default.

if (exists == False):
... if (field01.name != 'OBJECTID'):

newFields.append([field01.name, field01.type, field01.length])

Thanks again for the assistance!

Re: How to copy some fields from one feature class to an existing fc

MicahBabinski — Tue, 07 May 2019 20:39:10 GMT

Glad to hear it! Since sometimes OID fields have a name besides OBJECTID, an even more robust approach would be:

if (field01.type != 'OID'):‍

Happy scripting, Doug.