topic Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values? in Python Questions

ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

MichaelHutchison — Thu, 09 Mar 2017 15:38:25 GMT

I'm trying to label point features with ArcGIS Maplex Engine, using [field1], [field2], [field3], [datefield]. My code is set up to label [field1] + '\n' + [datefield][-2:]. If [field1] is null, it'll label [field2] + '\n' + [field3] + '\n' + [datefield][-2:]. For whatever reason, my code doesn't work if a feature has a null value in [datefield]. How do I tell my code if the [datefield] is null, label [field1] AND if [datefield] and [field1] is null, label [field2] + '\n' + [field3]? This is my code so far.

def FindLabel ( [field1], [field2], [field3], [datefield] 😞
if str([field1]) == "None" :
return [field2] + '\n' + [field3] + '\n' + [datefield][-2:]
elif str([field1]) != "None" :
return [field1] + '\n' + [datefield][-2:]

I tried adding this section but the engine doesn't seem to read it.

elif [datefield] == "None" :

return [field1]

elif [datefield] == "None" and str([field1]) == "None" :

return [field2] + '\n' + [field3]

My entire code is this.

elif [datefield] == "None" :

return [field1]

elif [datefield] == "None" and str([field1]) == "None" :

return [field2] + '\n' + [field3]

Thanks for the help.

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

IanMurray — Thu, 09 Mar 2017 15:49:21 GMT

Hi Michael.

I think your issue is that you are having it check again the string value "None" instead of a None object. Try checking it against the key word None instead of the string.

http://stackoverflow.com/questions/3289601/null-object-in-python

I suggest using the if ... is None format in the link for your syntax.

Regards,

Ian

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

MichaelHutchison — Thu, 09 Mar 2017 16:20:44 GMT

I tried simplifying it for testing purposes and it did not work for me.

def FindLabel ( [FIELD1], [DATEFIELD] 😞

if [DATEFIELD] is None :

return [FIELD1]

Am I missing something?

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

IanMurray — Thu, 09 Mar 2017 16:32:13 GMT

Actually it doing exactly what you are telling it to do. You said if it is a NULL label it a NULL which is nothing.

To test if its working I tried having it return something if it was Null:

def FindLabel ( [gasonsite] 😞
if [gasonsite] is None:
return "Value is Null"

I had dataset with some NULL values in a field and this expression successfully returned my string for the features that had NULL in that field. When I used the expression you used, it was blank like your probably was.

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

IanMurray — Thu, 09 Mar 2017 16:42:01 GMT

I thought about a good way to check and not add Null values to a label expression and here is a sample I used in ArcMap.

def FindLabel ( [gasonsite], [featuredlabel], [poweronsite]   😞
fields = ([gasonsite] , [featuredlabel] , [poweronsite])
label = ""
for field in fields:
    if field is None:
      continue
    else:
      label = label + field + "\n"
return label

If the value is Null, it add nothing to the label, it is has a value, add it to the label to be returned and add a carriage return.

Please note all my fields I used were strings and if you are using other types you will need to use the str() to convert them prior to concatenating.

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

TedKowal — Sun, 12 Dec 2021 00:14:37 GMT

I ran a quick test with two date fields Birthdate and Expiredate from one of my datasets .....

def FindLabel ( [BirthDate], [ExpireDate]  ):
  FindLabel = ""
  if [BirthDate] is None:
    FindLabel = "Null" + '\n'
  else:
    FindLabel = [BirthDate] + '\n'
  if [ExpireDate] is None:
    FindLabel = FindLabel + "Null2" + '\n'
  else:
    FindLabel = FindLabel + [ExpireDate] + '\n'
  return FindLabel + "Finished Dates"‍‍‍‍‍‍‍‍‍‍‍

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

RandyBurton — Sun, 12 Dec 2021 00:14:40 GMT

Perhaps a variation of this:

field1 = None # "Field1"
field2 = "Field2"
field3 = None # "Field3"
datefield = None # "2014-12-13"

if ( (field1 != None) and (datefield != None) ):
    print field1 + '\n' + datefield[-2:]  
elif (datefield != None):
    print '\n'.join(filter(None,(field2, field3, datefield[-2:])))
else:
    print '\n'.join(filter(None,(field2, field3)))
‍‍‍‍‍‍‍‍‍‍‍

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

DanPatterson_Retired — Fri, 10 Mar 2017 01:34:29 GMT

point raised before, but it is going to be more important in 3.x for future-proofing, because semantically there is only one None, so it is or isn't, hence nothing else can, or cannot be equal to it

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

RandyBurton — Sun, 12 Dec 2021 00:14:42 GMT

What about using:

if field1:
   do something‍‍

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

DanPatterson_Retired — Sun, 12 Dec 2021 00:14:45 GMT

True, but I don't like to equate None with 'empty'... again preference and semantics and how booleans are created. I sometimes prefer to check for an object type (ie the NoneType) versus and object's state (ie an empty list)a

field1 = None
if field1:
    print("is not None")
else:
    print("is not necessarily None")
    
is not necessarily None

field1 = []
if field1:
    print("is not None")
else:
    print("is not necessarily None")
    
is not necessarily None‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

As in this case...

field1 = None
if isinstance(field1, (type(None), list, tuple)):
    print("could be None")
else:
    print("is not necessarily None")
    
could be None‍‍‍‍‍‍‍

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

TedKowal — Fri, 10 Mar 2017 16:50:34 GMT

One of my last resort tests when nothing else seems to work is equating null to blank

myfield1 = [Field1]+""

if myfield1.strip() = "" then

'This could be null'

.....

"Python Nulls Strike back!"

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

RandyBurton — Sun, 12 Dec 2021 00:14:48 GMT

I received an error with this:

field1 = None
myfield = field1+""
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'‍‍‍‍‍

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

DanPatterson_Retired — Fri, 10 Mar 2017 18:05:03 GMT

Ted is maybe using so VB voodoo or the file doesn't contain None's but empty strings. so you would have to do

str(field1) + "" which is pretty useless when you can check for NoneType and/or empty anything with the added conversion.

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

RandyBurton — Sun, 12 Dec 2021 00:14:50 GMT

Back to Michael's question. Check for type None and an empty (zero-length) string.

field1 = "" # "Field1"
field2 = "Field2"
field3 = "" # "Field3"
datefield = "2014-12-13"


if (field1 is not None):
    # check for empty string (assuming field1 is a string type)
    if not len(field1):
        field1 = None
        print "field1 set to none"
# perhaps a similar check for datefield, etc.


if ( (field1 is not None) and (datefield is not None) ):
    print field1 + '\n' + datefield[-2:]  
elif (datefield is not None):
    print '\n'.join(filter(None,(field2, field3, datefield[-2:])))
else:
    print '\n'.join(filter(None,(field2, field3)))‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

RandyBurton — Sun, 12 Dec 2021 00:14:53 GMT

And other issues possible with str(None) which equals "None":

field1 = None
myfield = str(field1)+""
print len(myfield), myfield

4 None
‍‍‍‍‍

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

IanMurray — Fri, 10 Mar 2017 19:13:27 GMT

I don't recall him worried about empty strings, just null attribute table values causing issues in the label. Anyone have fault with my method I posted above?

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

RandyBurton — Fri, 10 Mar 2017 19:49:32 GMT

Sorry, I may have gotten off topic. It was just to clarify the difference between null, type None, and an empty string.

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

DanPatterson_Retired — Fri, 10 Mar 2017 21:56:01 GMT

I never endorsed the str(None) at all, Randy, just too many things that can be exceptions. Basically with tabular data, work with either checks for the empty string or None using isinstance. This covers shapefiles, file gdb's and numpy, scipy, matplotlib, etc etc at least... everything else is (server stuff etc) is on its own for me

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

TedKowal — Mon, 13 Mar 2017 15:07:18 GMT

... sorry did not convert to Python'ese '-'.join(filter(bool,(field1,"")))

--- and no it is not recommended only if the trustworthy None does not work (field contains unprintable artifact values).

Re: ArcGIS Maplex Python Labeling: If a value in a date field is null, how do I still show other values?

TedKowal — Mon, 13 Mar 2017 15:33:11 GMT

Like you I thought this turned into a case where None simply does not work as expected ... I do run across that quite often when I deal with data from multiple sources and platforms ....

... It is an important distinction knowing Null from Empty String.

max(None,"") #Returns blank

max("Hello","") #Returns Hello

Helps me quickly determine Nulls and Empty stings ....