Catching and re-using field properties correctly with ArcPy?

Question

I'm going through a feature class and attempting to catch all the fields and their properties, and reuse them in a new output feature class. Because I'm doing some stuff to the original data in-between, arcpy.CopyFeatures_management() doesn't work for me here.

My code:

in_fc = <the feature class>
d = arcpy.Describe(in_fc)
in_sr = d.spatialReference
in_fc_name = d.baseName

out_path = "C:/Temp/temp.gdb"
out_fc_name = f"{d.baseName}_edit"

out_fields = []
fields = arcpy.ListFields(in_fc)
for f in fields:
    if f.type == "String":
        field = [f.baseName, f.type, f.aliasName, f.length]
        out_fields.append(field)
    else:
        field = [f.baseName, f.type, f.aliasName, f.precision]
        out_fields.append(field)

# sanity check
for field in out_fields:
    print(field)  # all looks fine

out_fc = arcpy.CreateFeatureclass_management(proj_db, out_fc_name, f"{d.shapeType.upper()}", spatial_reference=in_sr)  # works

arcpy.AddFields_management(out_fc, fields)  # doesn't work

Fails with a convertArcObjectToPythonObject(gp.AddFields_management(*gp_fixargs((in_table, field_description), True))) and a runtime error.

Since the fields appear correct, and since the ArcPy documentation indicates that the Field type property is mapped to the AddFields_management() type parameter, (meaning I should be able to pass in "String" and have it parsed as "TEXT") I'm not sure where this is going wrong.

Answer 1

It seems you can skip the arcpy.AddFields_management() step if you simply include the template parameter in the arcpy.CreateFeatureclass_management() step.

Here is my test code, modified:

import arcpy
import os

proj_db = r"C:\Temp\project_database.gdb"
in_fc = r"C:\Temp\test_test123.gdb\test"
d = arcpy.Describe(in_fc)
in_sr = d.spatialReference
in_fc_name = d.baseName

out_fc_name = f"{d.baseName}_edit"
    
out_fc = arcpy.CreateFeatureclass_management(
        proj_db, 
        out_fc_name, 
        f"{d.shapeType.upper()}", 
        spatial_reference=in_sr, 
        template=in_fc
        ) 

Answer 2

First of all you are are looping through the fields adding to a list called out_fields but then you feed in the list fields into the AddFields tool...

Look at the Parameters section of the help file for the AddFields tool. What are you adding (or should say had intended to add)? Now look again at the Parameters section of the Field Properties and what does it actually want? A ValueTable not a list of lists.