Labelling using Python Parser in ArcGIS Desktop?

Question

I have limited expertise with Python.

I need to create labels based on groups of attributes. I've figured out a clumsy way to accomplish this but it involves 20 different annotation classes / SQL queries / label expressions, and I really hope there is a way to accomplish this more elegantly and efficiently, ideally with just 1 label expression.

My input data (which cannot be altered) is a feature class with 3 relevant fields (which I've made generic here).

• Codelist - numeric codes
• Attribute1 - an attribute
• Attribute2 - a second attribute

Codelist contains 100 numbers. Groups of these numbers require one label - for example codes 1,3,35,7,8 would get the label "Christmas, Attribute1, Attribute2" on 3 separate lines. Codes 2,9,34,100,54,22 would get the label "Easter, Attribute 1, Attribute2" on 3 separate lines. Etc etc.

I can't figure out how to use an SQL-like 'if [CODELIST] in (1,3,35,7,8):' statement in the Python label expression builder.

Is it possible?

Am I approaching this the right way or is my first effort using multiple annotation classes and SQL queries the best way to do this after all?

Answer 1

So, it depends. If you need the labels to look different (one needs to be green text, another large bold black), or if you need to manage label placement properties (one needs to be above a line the other below a line), or if you need to affect label/feature weights and/or label draw order, or if you need to manage any other label settings/properties separately for the different groups, then you will need to use separate label classes with SQL Queries on the classes as you are doing.

That said, if you are wanting to label all of the features essentially the same except for the actual text of the label, you can accomplish that with an advanced label expression as well depicted in @Dan's answer. However, an important note about using the python parser for an advanced label expression where you are looking at numeric values:

From my testing (ArcMap 10.5.1), it appears that the label expression will read all values, INCLUDING numeric ones, as strings. So use essentially what @Dan posted, except you will likely have to modify the `in (...) from what you would expect; possibly use code similar to the following.

def FindLabel ([Codelist],[Attribute1],[Attribute2]):
  if [Codelist] in ('1','3','35','7','8'):
    return 'Christmas\n'+[Attribute1]+'\n'+[Attribute2]
  elif [Codelist] in ('2','9','34','100','54','22'):
    return 'Easter\n'+[Attribute1]+'\n'+[Attribute2]
  elif ...
    return ...
  else:
    return 'No holiday\n'+[Attribute1]+'\n'+[Attribute2]

Note: I included an else: at the end with a return statement after it. You would use that if you wanted to return a specific string when the [Codelist] field doesn't match any the criteria you've previously provided in the above if and elif statements. If you don't need that, you can leave those last 2 lines off.

Answer 2

Yes, it's possible. Tick the Advanced option in the Label Expression dialog box.

Then add your labelling conditions in the code block.

In my case, I used the following code block (which you can adapt to your situation).

def FindLabel ( [Report_FC], [Report_Group], [Request_UFI]):
  if [Report_Group] in ('Administration', 'Information'):
    return [Report_FC]
  if [Report_Group] == 'Infrastructure':
    return [Request_UFI] 

To get three attributes back with a new line between each you would use:

return "{}\n{}\n{}".format([Attrib1], [Attrib2], [Attrib3])

or in your case:

return "{}\n{}\n{}".format("Christmas", [Attrib1], [Attrib2])