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

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04-25-2019 09:16 AM
DougWolfinger2
New Contributor II

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
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6 Replies
LeonardoMontero
New Contributor III

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

DougWolfinger2
New Contributor II

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]))

...

Runtime error Traceback (most recent call last): File "<string>", line 22, 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 removed field[0] and field[1], then got this error:

Runtime error Traceback (most recent call last): File "<string>", line 22, in <module> File "j:\apps\arcgis\desktop10.4\arcpy\arcpy\management.py", line 3149, in AddField raise e ExecuteError: ERROR 000310: The Field name must not start with a number

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

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MicahBabinski
Regular Contributor

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

DougWolfinger2
New Contributor II

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!

MicahBabinski
Regular Contributor

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.

LeonardoMontero
New Contributor III

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