topic Re: Conditioning labels in Python Questions

Conditioning labels

Ulises — Sun, 12 Dec 2021 07:12:24 GMT

Hi everyone,

I'm trying to define an expression for labeling parcel polygons in ArcMap. The feature class has 3 attributes of interest: CATEGORIA, NUM_CATASTRO, and PARCEL_SP. If CATEGORIA (integer field with subtypes defined) is not 0 (N/A), then label the polygon with the value in PARCEL_SP, otherwise label with NUM_CATASTRO. I'm not a programmer and I'm just starting with Python so I'm not sure what is missing. So far I have...

def FindLabel (  [CATEGORIA],[NUM_CATASTRO], [PARCEL_SP] ):
  if [CATEGORIA] ==0:
    return [PARCEL_SP]
  else:
    return  [NUM_CATASTRO]

The issue is that I can see labels for NUM_CATASTRO where they should, but none for PARCEL_SP.

If I reverse the values...

def FindLabel (  [CATEGORIA],[NUM_CATASTRO], [PARCEL_SP] ):
  if [CATEGORIA] ==0:
    return  [NUM_CATASTRO]
  else:
    return [PARCEL_SP]

it labels the PARCEL_SP where is supposed to but not the NUM_CATASTRO.

Same thing using the following statement...

def FindLabel (  [CATEGORIA],[NUM_CATASTRO], [PARCEL_SP] ):
  if [CATEGORIA] !=0:
    return   [PARCEL_SP]
  else:
    return  [NUM_CATASTRO]

Any help will be appreciated...

Thanks

Re: Conditioning labels

TomSellsted — Tue, 10 Feb 2015 19:30:25 GMT

Greeting Ulises!

It is most likely that the values in [CATEGORIA] are not what you are expecting them to be in python. If the field is not numeric, it will never evaluate to 0, but a text value of "0". It may be a Null value and again it would not evaluate to be 0. Your logic looks sound, please check the values and make sure it is the right field type.

Regards,

Tom

Re: Conditioning labels

Ulises — Tue, 10 Feb 2015 19:38:03 GMT

Thanks for the reply, Tom.

Field CATEGORIA is numeric, yet I'm assuming is behaving like it isn't, yet haven't been able to identify why.

Re: Conditioning labels

TomSellsted — Tue, 10 Feb 2015 19:41:07 GMT

Ulises,

Are there 0 values in the field [CATEGORIA] or could it be a value of null?

Regards,

Tom

Re: Conditioning labels

Ulises — Tue, 10 Feb 2015 19:45:09 GMT

No null values...

Re: Conditioning labels

TomSellsted — Tue, 10 Feb 2015 19:52:21 GMT

Ulises,

It looks like python automatically casts numeric field values as strings, so you would need to change your expression to

if [CATEGORIA] == "0":

if int([CATEGORIA]) == 0:

Re: Conditioning labels

Ulises — Tue, 10 Feb 2015 20:08:01 GMT

Thanks again. Is not working either way. First suggestion "0" still behaves as mentioned earlier and second option (using int) returned an error...

ValueError: invalid literal for int() with base 10:'N/A'

N/A is the descriptive value for the subtype coded with the integer 0. Also changed the expression to evaluate against "N/A" with no success.

Re: Conditioning labels

Zeke — Tue, 10 Feb 2015 20:53:49 GMT

I don't think python would be casting numeric data types to strings. That doesn't make sense.

Re: Conditioning labels

Zeke — Tue, 10 Feb 2015 20:58:06 GMT

Maybe post a screenshot of part of your attribute table.

Re: Conditioning labels

TedKowal — Sun, 12 Dec 2021 07:12:26 GMT

Your logic look good!

If you are sure that your Catagoria is numeric not null ect..... Then have tried another logical method such as :

def FindLabel (  [CATEGORIA],[NUM_CATASTRO], [PARCEL_SP] ):  
  if [CATEGORIA] > 0:  
    return [PARCEL_SP]  
  else:  
    return  [NUM_CATASTRO]

Re: Conditioning labels

TomSellsted — Tue, 10 Feb 2015 21:01:20 GMT

Greg,

That is straight from the "Building Label Expressions" in the ArcGIS Documentation. I did a test on my data and it absolutely does cast the field values into strings.

Regards,

Tom

Re: Conditioning labels

Ulises — Sun, 12 Dec 2021 07:12:29 GMT

I tried with VBScript and it worked. After banging my head for a while against the monitor I decided to try one last thing before a break...RESTART ArcMap.

Then get back to Python and tried again...IT WORKED!!!

Don't really know what happened, but Tom's suggestion make me try using the string value for the subtype instead of the number and it worked. The final code is like this...

def FindLabel (  [CATEGORIA],[NUM_CATASTRO], [PARCEL_SP] ):
  if [CATEGORIA] =='N/A':
    return  [NUM_CATASTRO]
  else:
    return "<CLR red='255'><FNT size = '10'>" +  [CATEGORIA] + "</FNT></CLR> <CLR blue='255'> \n" + [PARCEL_SP] + "</CLR>"

Find it weird that I needed to use the description instead of the integer value for the subtype field.

Thanks again for the help and suggestions.

Re: Conditioning labels

TomSellsted — Tue, 10 Feb 2015 21:06:41 GMT

Ulises,

Perfect! Glad that worked for you! Please mark the answer as correct too!

Regards,

Tom