I'm trying to use an if statement in the field calculator: This is what the code looks like in Python:

a= 2 
if a%2==0:

print MH_ID_Calc


so I tried to run that in ArcGIS field calculator:

def myCalc(FID,FACID):
if FID%2==0:
return FACID[0:6]
return FACID[7:14]


But it fails each time.

  • Welcome to GIS SE! As a new user please take the tour to learn about our focused Question and Answer format. Please check your indentation - there are no indents in your field calculator code above, but python needs the indents. Also double-check that you've selected the Python Parser in field calculator.
    – Midavalo
    Feb 1, 2017 at 20:52
  • 1
    What happens when you run the field calculator? There should be result messages under Geoprocessing > Results
    – Midavalo
    Feb 1, 2017 at 20:53
  • Check out this question and answer which probably makes this a duplicate.
    – mkennedy
    Feb 1, 2017 at 21:18
  • 3
    myCalc(!FID!, !FACILITYID!)? There's a comma missing when you call the function
    – Bjorn
    Feb 1, 2017 at 21:43
  • Please edit your question to include the error message.
    – Aaron
    Feb 1, 2017 at 22:33

1 Answer 1


As others have already commented, the parameters of the function call in your expression should be comma separated:


And you must use correct indentation with Python (unlike other languages, this is part of Python syntax, and it will not work if the indentation is not correct):

def myCalc(FID,FACID):
    if FID%2==0:
        return FACID[0:6]
        return FACID[7:14]

Ie, anywhere that a line ends with a colon (:) represents a new code block and the next line should be indented further. All lines within a block must have exactly the same indentation, unless they are part of a sub-block, in which case, they must have the exact same indentation as the other lines a the same level of that sub-block.

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