topic Re: Thousands Separator for Label Expression using Python in Python Questions

Thousands Separator for Label Expression using Python

ChrisDonohue__GISP — Thu, 20 Oct 2016 18:52:15 GMT

How does one use Python to format a number label so it shows the thousands separator? For example, I have a value of 12345 that I want to display (from the Shape.Area field of a File Geodatabase feature class) on the map as a label as 12,345.

I looked at these discussions, but can't seem to get it to work.

What is label expression for formatting a number to have thousands separator and decimals?

python - Add 'decimal-mark' thousands separators to a number - Stack Overflow

I guess I could slice the value and insert commas, but I was hoping to use something easier.

I'm using ArcGIS 10.2.1 (so Python 2.7.5). I'm a beginner in Python, so there is a good chance I am just missing something basic in trying to do this.

Chris Donohue, GISP

Re: Thousands Separator for Label Expression using Python

DanPatterson_Retired — Thu, 20 Oct 2016 18:55:29 GMT

>>> "{:,}".format(1000000)
'1,000,000'

Re: Thousands Separator for Label Expression using Python

BrittneyWhite1 — Thu, 20 Oct 2016 19:18:28 GMT

From Building label expressions: "Field values are automatically cast to text strings. Therefore, if you wish to use a numeric value in an arithmetic operation, or when making a comparison, you will need to cast it back to a numeric data type."

This could look something like:

"{:,}".format(float([Field_Name]) )

Re: Thousands Separator for Label Expression using Python

ChrisDonohue__GISP — Thu, 20 Oct 2016 20:09:43 GMT

If I purely use a number in the format, it works correctly. But now the catch, how do I substitute in SHAPE_Area so it labels based on that field that with comma separators instead of a hard-coded number?

Chris Donohue, GISP

Re: Thousands Separator for Label Expression using Python

DanPatterson_Retired — Thu, 20 Oct 2016 22:14:19 GMT

python parser.... then why are the fieldnames enclosed in square brackets instead of ! ! ?? Is this unique to labelling? Chris, I don't do much labelling, but did you pick the parser before building the expression or after? and what's up with the one space indentation? does Arc* put that indentation in or is that you?

Re: Thousands Separator for Label Expression using Python

ChrisDonohue__GISP — Thu, 20 Oct 2016 22:48:37 GMT

I was noticing that too. It doesn't matter if the Parser in the Label Expression is changed to Python first or not, the field names come across with brackets when one double-clicks on the field you want to select it. On top of that, if one changes the field name to be surrounded by exclamation marks instead of brackets(with Python still selected as the Parser) it errors out:

As for the one-space indentation, it is actually two spaces and that seems to be what ArcGIS defaults to.

Chris Donohue, GISP

Re: Thousands Separator for Label Expression using Python

DanPatterson_Retired — Thu, 20 Oct 2016 22:54:52 GMT

so even str(!SHAPE_area!) errors out? I am just wondering if the output is supposed to be string.

In any event, I don't do labelling, but I would be a tad peeved if Verify says nothing about what was wrong and more importantly, if the python parser is defective. Good luck

Re: Thousands Separator for Label Expression using Python

DarrenWiens2 — Sat, 11 Dec 2021 17:59:28 GMT

Hmmm... this works for me (field type is Long):

def FindLabel ( [CLIENTNUM] ):
  return "{:,}".format(float([CLIENTNUM]))‍‍

Re: Thousands Separator for Label Expression using Python

DanPatterson_Retired — Thu, 20 Oct 2016 23:04:21 GMT

was that with the python parser and selecting the fields from the list? or by keying everything in? That is one of the things Chris needs to figure out ... is it the process that is causing the error or the parser?

Re: Thousands Separator for Label Expression using Python

DarrenWiens2 — Thu, 20 Oct 2016 23:20:35 GMT

Python parser, and I don't recall if I selected from the list or not, but it's correct. The label expression box doesn't use the normal !Field! notation, just to keep you on your toes.

Re: Thousands Separator for Label Expression using Python

DanPatterson_Retired — Thu, 20 Oct 2016 23:24:31 GMT

good catch if it works from the list selection...

I would deem this an appropriate use of 'pythonesque', perhaps VBthon?

Re: Thousands Separator for Label Expression using Python

ChrisDonohue__GISP — Fri, 21 Oct 2016 14:37:13 GMT

That worked! Thanks Darren.

Chris Donohue, GISP

Re: Thousands Separator for Label Expression using Python

ChrisDonohue__GISP — Fri, 21 Oct 2016 14:39:04 GMT

"The label expression box doesn't use the normal !Field! notation, just to keep you on your toes."

Good catch. The whole lack of !Field! notation despite being in the Python mode was making me wonder if my software was corrupted. Maybe we could submit this to ArcGIS Ideas to standardize this so folks won't be confused?

Chris Donohue, GISP

Re: Thousands Separator for Label Expression using Python

ChrisDonohue__GISP — Fri, 21 Oct 2016 14:48:01 GMT

Monty Python, in search of the holy code:

"But you're VB! What are you doing in the Python Parser?"

Chris Donohue, GISP

Re: Thousands Separator for Label Expression using Python

DanPatterson_Retired — Fri, 21 Oct 2016 17:13:40 GMT

that is a bug... if it advertised as python, it should behave lie python, there should be non 'esque' in parsers there is enough of that in the various database forms

Re: Thousands Separator for Label Expression using Python

ClintonDow1 — Fri, 21 Oct 2016 22:09:19 GMT

Hi Chris,

The cast is necessary because the field's value is returned as an object (that is, the Python base class), since arbitrary data types are supported by the expression dialog. String.format() does not work with uncast objects because an object.__repr__ method returns a 'method-wrapper' class and not a datatype that string.format knows how to work with. Once you've cast the object, in this case invoking its __float__ method, it returns its value as a float data type which plays nice with string formatting.

Re: Thousands Separator for Label Expression using Python

DanPatterson_Retired — Fri, 21 Oct 2016 22:18:17 GMT

Clinton, this would be a nice inclusion in the help topics. It may not matter for most, but if casting is needed because a python object is used, then this means something to some of us.

This is going to be an issue when people start migrating to Pro and start using Pandas which makes judicious use of python's object... most people will think

... if it looks like a number, it should act like a number...

Indicating in the help that casting to float or string (I wont get into python 2 vs 3 'strings') should be used explicitly would at least warn people. A few simple examples would also help. I know that you aren't the person to implement this in the help, but I have a strong suspicion that the doc's people aren't big on object casting and representation.

Thanks

Re: Thousands Separator for Label Expression using Python

ClintonDow1 — Fri, 21 Oct 2016 22:29:21 GMT

Hi Dan, I agree. I had to do a bit of digging to figure that out so I don't think its common knowledge but I'll definitely recommend that we mention it in the docs.