topic Python Label Expression in Python Questions

Python Label Expression

ScottLamon1 — Thu, 30 Apr 2015 16:36:15 GMT

I am trying to create a python label expression without having any python skills

I have 2 fields [FIELD1] and [FIELD2]

If [FIELD1] > 0 and [FIELD2] < 0

return "text:" [FIELD1] 'text:" [FIELD2]

If [FIELD1] > 0 and [FIELD2] !< 0

return "text:" [FIELD1]

If [FIELD1] !> 0 and [FIELD2] < 0

return 'text:" [FIELD2]

Any help would be greatly appreciated.

Re: Python Label Expression

DarrenWiens2 — Thu, 30 Apr 2015 16:42:50 GMT

Please refer to this help page as a start for building label expressions, and this post for posting code blocks.

Re: Python Label Expression

DanPatterson_Retired — Thu, 30 Apr 2015 16:57:46 GMT

Header 1	Header 2
If [FIELD1] > 0 and [FIELD2] < 0 return "text:" [FIELD1] 'text:" [FIELD2]	if (!FIELD1! > 0) and (!FIELD2! < 0): out = str(!FIELD1!) + str(!FIELD2!)
If [FIELD1] > 0 and [FIELD2] !< 0 return "text:" [FIELD1]	elif (!FIELD1! > 0) and (!FIELD2! != 0): out = str(!FIELD1!)
If [FIELD1] !> 0 and [FIELD2] < 0 return 'text:" [FIELD2]	elif (!FIELD1! > 0) and (!FIELD2! != 0): out = str(!FIELD1!)
	else out = "no match'
	return out

Header 1

Header 2

If [FIELD1] > 0 and [FIELD2] < 0

return "text:" [FIELD1] 'text:" [FIELD2]

if (!FIELD1! > 0) and (!FIELD2! < 0):

out = str(!FIELD1!) + str(!FIELD2!)

If [FIELD1] > 0 and [FIELD2] !< 0

return "text:" [FIELD1]

elif (!FIELD1! > 0) and (!FIELD2! != 0):

out = str(!FIELD1!)

If [FIELD1] !> 0 and [FIELD2] < 0

return 'text:" [FIELD2]

elif (!FIELD1! > 0) and (!FIELD2! != 0):

out = str(!FIELD1!)

else

out = "no match'

return out

Lets break this down into parts

Toggle on the Python parser, in the field calculator. The results must be put into a text field.

So as python code it becomes with 4 spaces for indents.

def check_cond(a,b):

"""two fields as input, """

if a > 0) and b < 0):

out = str(!FIELD1!) + str(!FIELD2!)

elif a > 0) and b != 0):

out = str(!FIELD1!)

elif a > 0) and b != 0):

out = str(a)

else

out = "no match'

return out

Expression box

check_cond(!FIELD1!,!FIELD2!)

Always check the unexpected, never return prematurely, hence return out should be the last line

Re: Python Label Expression

DarrenWiens2 — Sat, 11 Dec 2021 14:42:15 GMT

There are a few tricky little things, so here goes. I don't believe there is such thing as !<, use >= instead. You can't concatenate numbers to strings, cast to string using str(). You'll have to decide if you really mean "if, if, if" or "if, elif, elif" - either can be used if you know what it means.

def FindLabel ( [Field1] , [Field2]  ):
    if [Field1] > 0 and [Field2] < 0:
        return "text: " + str( [Field1] )+ " text: " + str( [Field2] )
    if [Field1] > 0 and [Field2] >= 0:
        text = "text: " + str([Field1] )
        return text
    if [Field1] <= 0 and [Field2] < 0:
        return "text: " + str( [Field2] )

Re: Python Label Expression

DarrenWiens2 — Thu, 30 Apr 2015 17:14:42 GMT

Just a note that this is a field calculator expression, not label expression, which is quite different. Of course, you could calculate the label to a new field, but that's an added step.

Re: Python Label Expression

SepheFox — Thu, 30 Apr 2015 17:54:09 GMT

You could also define label classes based on those if statements, and then label each class accordingly.

Re: Python Label Expression

ScottLamon1 — Thu, 30 Apr 2015 22:35:35 GMT

I went with the various label classes. Thanks for all the info though.

Re: Python Label Expression

SepheFox — Thu, 30 Apr 2015 23:30:19 GMT

I'm glad you found a solution that worked for you, Scott. Do you mind marking this questions as answered? This accomplishes a couple of things: people will realize that you don't still need help, and also, other people in the future with the same question can find the answer easier. Thanks!

Re: Python Label Expression

curtvprice — Fri, 01 May 2015 01:12:53 GMT

I'm a moderator and marked your suggestion correct.

Re: Python Label Expression

SepheFox — Fri, 01 May 2015 01:13:41 GMT

Thanks Curtis!