topic Re: Python Label Expression in Python Questions

Python Label Expression

BartonGriesenauer — Tue, 01 Oct 2013 19:36:39 GMT

I am trying to create one label expression that has two label options. The first option will stack the parcel number on top of the lot number and the other option would stack the parcel number on top of deeded acreage. The [LOTNUMBER] field, [PARCEL] field, are text fields the [DEEDACRES] is a double. I have no python experience, did not think this expression would be this difficult to come up with. I would appreciate any help.

def FindLabel ( [PARCEL] , [LOTNUMBER] , [DEEDACRES] 😞
if long([LOTNUMBER]) >1:
return "<CLR yellow='255'>" + [PARCEL] + "</CLR>" + '\n' + [LOTNUMBER]
else:
return "<CLR yellow='255'>" + [PARCEL] + "</CLR>" + '\n' + [DEEDACRES]

Re: Python Label Expression

T__WayneWhitley — Tue, 01 Oct 2013 19:59:09 GMT

..at the very least, don't you have to convert the double to string? Use 'str'

Re: Python Label Expression

T__WayneWhitley — Sat, 11 Dec 2021 15:14:28 GMT

...and don't forget your 'closing' formatting tags, this works fine for experimental purposes for me - could have just changed the label font to yellow instead of using text formatting tags, unless you have other label classes or something.

The below was just fiddling around to mimic the same design you had, where my ID field is numeric:

def FindLabel ( [NAME], [ID] , [RECHAR]  ):
     if long( [RECHAR].split('-')[0] )<=80000:
         return "<CLR yellow='255'>"+ [RECHAR] + '\n' +  [NAME] + "</CLR>" 
     elif long( [RECHAR].split('-')[0]) > 80000:
          return "<CLR yellow='255'>"+ [NAME] + '\n' + str( [ID] ) + "</CLR>"

Hope that helps - also when you post code (another example of text tags), it will display correctly if you select (highlight) your code section and use the hashtag symbol (#)...which simply should place the tags in...

 goes at the beginning, I think you get my drift, just reversed them here to negate the effect?

EDIT: Please don't apply the '.split('-')[0]' on your code -- I did that only on my data to coerce text into a val I can use 'long' on.

Enjoy,
Wayne

Re: Python Label Expression

MattSayler — Sat, 11 Dec 2021 15:14:31 GMT

To elaborate on what Wayne is saying, fields that are one of the numerical data types (long integer, short integer, double, float) can't be concatenated with strings (it's akin to asking the interpreter what number the letter "a" + 1 evaluates to). Use the built in str() method to convert numbers to strings and then it will be able to put them together (i.e. "a" + str(1) == "a" + "1" == "a1").

So if the data types for [LOTNUMBER] and [DEEDACRES] are numerical, something like this:

def FindLabel ( [PARCEL] , [LOTNUMBER] , [DEEDACRES] ):
  if long([LOTNUMBER]) >1:
    return "<CLR yellow='255'>" +  [PARCEL] + "</CLR>" + '\n' + str([LOTNUMBER])
  else:
    return "<CLR yellow='255'>" +  [PARCEL] + "</CLR>" + '\n' + str([DEEDACRES])

Re: Python Label Expression

T__WayneWhitley — Tue, 01 Oct 2013 21:03:16 GMT

ha ha, yes, very well put, Matt! Excellent.

Re: Python Label Expression

BartonGriesenauer — Wed, 02 Oct 2013 17:02:31 GMT

First off, thank you for all your help. I am not even a novice at Python, so I don't think I stated my initial question very well. I want to label the parcels that are lots one way and the metes & bounds parcels another way. I want to label the parcels that are lots, the lot field is not null, as parcel stacked on top of lot number. I want to label the parcels that are not lots, the lot field is null, as parcel stacked on top of deeded acreage. I tried both your solutions and still the parcels that are not lots are not getting labelled at all. My PARCEL and LOTNUMBER fields are text fields. DEEDACRES is a double field. I apologize for any confusion.

Re: Python Label Expression

MattSayler — Sat, 11 Dec 2021 15:14:34 GMT

How about:

def FindLabel ( [PARCEL] , [LOTNUMBER] , [DEEDACRES] ):
  if [LOTNUMBER].strip() == None:
    return "<CLR yellow='255'>" + [PARCEL] + "</CLR>\n" + str([DEEDACRES])
  else:
    return "<CLR yellow='255'>" + [PARCEL] + "</CLR>\n" + [LOTNUMBER]

Re: Python Label Expression

BartonGriesenauer — Wed, 02 Oct 2013 17:28:38 GMT

Still not labeling parcels with null lot number attributes. I have attached a screen capture.

Re: Python Label Expression

MatthewDobson — Sat, 11 Dec 2021 15:14:36 GMT

Won't "not" work? I haven't corrected for your specific example, but what about something like:

def FindLabel ( [contractorName] ):
  if not [contractorName]:
    a = "Apples"
  else:
    a = [contractorName]
  return a

Re: Python Label Expression

MatthewDobson — Sat, 11 Dec 2021 15:14:39 GMT

Or using 'not' ....

def FindLabel ( [PARCEL] , [LOTNUMBER] , [DEEDACRES] ):
  if not [LOTNUMBER]:
    return "<CLR yellow='255'>" + [PARCEL] + "</CLR>\n" + str([DEEDACRES])
  else:
    return "<CLR yellow='255'>" + [PARCEL] + "</CLR>\n" + [LOTNUMBER]

Re: Python Label Expression

BartonGriesenauer — Thu, 03 Oct 2013 11:11:24 GMT

Thank you very much for your help that did it!

Re: Python Label Expression

SiranErysian — Mon, 06 Oct 2014 16:44:18 GMT

I need assistance with labeling also. I am new to Python and I may have posted this but I am going to try to get your assistance on this since I've been reading your answers to this string from Barton.

I am trying to label contours that are designated as "major" which are the rounded number in the values fields--300, 350, 400, etc. and not label all of the contours. I've been in the Python mode, advanced checked in the label expression dialog box but how do I Find a label in one field and label it some value from another field? Is this possible?

Re: Python Label Expression

Zeke — Mon, 06 Oct 2014 20:30:26 GMT

Siran,

To label numbers divisible by 100, use the modulo operator. In the label expression advanced box, set the parser to Python. Then use a function like below:

def FindLabel(somefield):

if somefield % 100 == 0: return somefield

if you want to label with a different field based on somefield:

def FindLabel(somefield, anotherfield):

if somefield % 100 == 0: return anotherfield

Re: Python Label Expression

SiranErysian — Mon, 06 Oct 2014 20:42:31 GMT

this did not work:

I used 50% since I want to label every 50' contour

tried it without brackets around Contour also but it didn';t work.

Re: Python Label Expression

Zeke — Tue, 07 Oct 2014 12:32:27 GMT

You're not using 50%. You're using modulo 50; the modulo operator is the % sign in Python. It's like regular division, except it gives you the remainder.

Primarily though, you need parentheses around the field name in the first line - def FindLabel([Contour]):

You also need to see whether the expression if [Contour] % 50 == 0: You left the 0 out above.

Re: Python Label Expression

SiranErysian — Tue, 07 Oct 2014 15:21:27 GMT

Thanks. I re do and be more careful next time....