topic Re: List of fields in Python Questions

List of fields

GasperZupancic — Thu, 15 May 2014 13:33:08 GMT

Hallo!

I need to check if a feature class includes a field called 'unwanted_field' and then delete it. I've been trying to accomplish that with an if statement on a field list gained by the arcpy.ListFields tool, but with no success. If I type in my 10.2.1 ArcMap Python window next code:

arcpy.ListFields('my_feature_class')

I get the following result:

[<Field object at 0x57483b0[0x623f860]>, <Field object at 0x5748290[0x623ff20]>, <Field object at 0x57485b0[0x623fd10]>, <Field object at 0x114465d0[0x623ff80]>, <Field object at 0x5742ff0[0x623fda0]>, <Field object at 0x587d570[0x623f650]>, <Field object at 0x11446670[0x623fa10]>, <Field object at 0x11446630[0x623fea8]>]

even though my_feature_class includes 8 fields named: OBJECTID, SHAPE, Shape_Length, etc.

What am I doing wrong?

Thanks in advance,
Gašper

Re: List of fields

JamesCrandall — Sat, 11 Dec 2021 18:55:28 GMT

for fld in arcpy.ListFields('my_feature_class'):
  if fld.name == 'unwanted_field':
     'add field delete code here

Re: List of fields

IanMurray — Sat, 11 Dec 2021 18:55:30 GMT

You are doing nothing wrong, it just is printing the location on the harddrive of each field, instead of the name. If you need to retrieve the actual name of the field, you need to use the .baseName or .aliasName method on each field.

More on that can be found getting field attributes here: http://resources.arcgis.com/en/help/main/10.2/index.html#//018z0000004n000000

If you are writing in the interative python window, you'd probably want something like this if you wanted to just delete the "unwanted_field".

fieldlist = arcpy.ListFields('my_feature_class')
 
for field in fieldlist:
  if field.baseName == "unwanted_field":
    arcpy.DeleteField_management('my_feature_class", field)

Hope this helps

Edit: Oops looks like James beat me to it.

Re: List of fields

Zeke — Sat, 11 Dec 2021 18:55:33 GMT

Try something like:

# 1. list fields (from here)
import arcpy  
featureclass = "c:/data/municipal.gdb/hospitals" 
field_names = [f.name for f in arcpy.ListFields(featureclass)] 

# 2. another method
import arcpy
lstflds = arcpy.ListFields("yourfeatureclass")
for fld in lstflds:
    if fld.name == "somefield":
        arcpy.DeleteField_management("yourfeatureclass", "somefield")

# 3. simpler, if you know your feature class; no need to check field name, you provide it
arcpy.DeleteField_management("yourfeatureclass", "somefield")

Re: List of fields

AdamCox1 — Sat, 11 Dec 2021 18:55:36 GMT

Hi Gaspar, what you're getting is a list of field objects, which, when printed out, looks like gibberish. As jamesfreddyc wrote above, you need to access the name property of each field object. You can condense this by using list comprehension:

if "fieldname" in [f.name for f in arcpy.ListFields(featureclass)]:
    #do something

Lists and dictionaries are extremely useful, so it's good to get familiar with them https://docs.python.org/2/tutorial/datastructures.html

Re: List of fields

IanMurray — Thu, 15 May 2014 14:01:11 GMT

I think we had an overkill of responses for this thread.

Re: List of fields

AdamCox1 — Thu, 15 May 2014 14:03:44 GMT

I think we had an overkill of responses for this thread.

Yeah, I think they all happened simultaneously too.

Re: List of fields

GasperZupancic — Mon, 19 May 2014 04:57:33 GMT

Tkank you all!