1

I'm trying to fill a blank field depending on the contents of three other fields using python in the field calculator.

Sample code is something like:

def getClass(Text1,Text2,Text3):
  if Text1 is None:
    return Text2
  elif Text2 is None:
    return Text3      
  else:
    return Text1

I can retrieve the value of the first field but never the 2nd two. I know this isn't the right way but I can't figure out the nesting levels... Any ideas?

UPDATE: Fixed by stripping out the white space. Credit to this post Using Calculate Field tool to calculate on null fields?

def getClass(Text1,Text2,Text3):
  if Text1.strip():
    x = Text1
  elif Text2.strip():
    x = Text2    
  elif Text3.strip():
    x = Text3
  else:
    x = "NA";
  return x
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2
  • 1
    Are the Text fields actually Null, or just empty, i.e. '' ?
    – recurvata
    Jun 17, 2016 at 14:30
  • Text fields are empty ''
    – Josh J
    Jun 20, 2016 at 9:50

2 Answers 2

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1

Use the "not equal" operator for the field calculator. 

def getClass(Text1,Text2,Text3):
  if Text1 != None:
    return Text1
  elif Text2 != None:
    return Text2      
  elif Text3 != None:
    return Text3
  else:
    return None;

You may also want to account for the possibility that none of the input fields have a value, as seen in the code snippet I posted.

Also, checkout this post about the difference between using the "is" operator versus "==":

https://stackoverflow.com/questions/132988/is-there-a-difference-between-and-is-in-python

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5
  • @recurvata brings up a good point in the comment above. If you need to account for empty strings in place of <Null>, you could modify the boolean expressions like so ---> if Text1 != None and Text1 != "":
    – GeoJohn
    Jun 17, 2016 at 14:37
  • 2
    A simpler way would just be if Text1: -- Both None and empty strings '' are false-y values in Python.
    – Paul
    Jun 17, 2016 at 21:15
  • I've tried all of the options mentioned and they return Text1 but not Text2 or Text3. This is the same whether I use None or '' and != or if Text1:. Is this a job that field calculator can't handle and should I switch to arcpy instead?
    – Josh J
    Jun 20, 2016 at 10:00
  • Can't tell if you mean '' above or ' ' (an empty space) in your comment above. Empty space is likely incorrect. If no values are Null, testing for None won't help. '' or ' ' will always return Text1 in your code above, since '' and ' ' both != None; that is, your first test is always True, thereby returning Text1. Same with if Text1:
    – recurvata
    Jun 21, 2016 at 13:27
  • Fixed. Using this post gis.stackexchange.com/questions/81143/…
    – Josh J
    Jul 4, 2016 at 10:52
0

You need to make sure you're passing the other fields in the function call at the bottom. getClass(!Field1!, !Field2, !Field3!)

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