Delete Unnecessary Fields In Standalone Table Using Arcpy

Question

My question is similar to that I asked here. The script below, however, is intended to delete unnecessary fields from a single standalone table rather than a database full of tables. The answer in the question referenced above has not performed consistently and I am thinking narrowing it down to a single table may provide some insight to why this is so.

import arcpy
from arcpy import env

table_name = (r'C:\MyDatabase.gdb\StandAloneTable')
field_names = [f.name for f in arcpy.ListFields(table_name) if not f.required]
keep = True

with arcpy.da.SearchCursor(table_name, field_names) as cursor:  
    for row in cursor:
        v = row[0]
        if v is None or isinstance(v, basestring) and \
           (v == '<Null>' or \
            v == 0 or \
            v == '' or \
            v == ' ' or \
            v == '  '):
            keep = False
            break

    if keep is False:
        arcpy.DeleteField_management(table_name, field_names)

This script runs without error aside from failing to delete the fields populated only with the values identified in first if-statement as I had intended. No fields are being deleted. Any ideas on what I am doing wrong?

Also, while I am testing this script on standalone tables within a file GDB, the standalone tables I plan to eventually run this script for are housed within an ArcSDE geodatabase.

Answer 1

I think the reason nothing is being deleted may be because you break the with and you're not even hitting your if keep is False:

You may want to outdent (un-indent) your if block.

Note: That said, I believe that if you change this if you will delete ALL fields in your field_names as you are not restricting to a single field or a specific list of fields to delete. arcpy.DeleteField_management(table_name, field_names) will delete all fields in field_names and this list hasn't been updated.

The answer in your linked question loops through the fields, and restricts the deletion to just the current field.

for field in field_names:

---

Doing a quick edit on your linked answer, this should work (although I'm not a fan of setting keep = False first as this runs the risk of deleting a field if something weird happens and the if block doesn't find a valid value):

import os
import arcpy
arcpy.env.workspace = r'C:\MyDatabase.gdb'
table_name = (r'StandAloneTable')
field_names = [f.name for f in arcpy.ListFields(table_name) if not f.required]

# Iterate over the fields
for field in field_names:
    # Set a test variable to False
    keep = False
    # Iterate over each feature; if it has a non-null value, then set
    #   the test variable to True and then break out of the cursor
    with arcpy.da.SearchCursor(table_name, field) as cursor:
        for row in cursor:
            v = row[0]
            if v is not None or \
              (isinstance(v, basestring) \
              and (v.lower.strip() != ''\
                or v != '<null>')):
                keep = True
                break

    # If the test variable was unchanged, delete the field
    if keep is False:
        arcpy.DeleteField_management(fc, field)