Field Calclator Issue (if Statement?)

ColterSikora1

Hello All,

I am trying to fill data in a field through Model Builder which requires me to concatenate data from two fields and then separate the data with a hyphen.  The issue I have is that in many cases, the second field has no data and thus, there is no point to having a hyphen.  Is there a relatively simple if statement that could handle this issue?

Thank you for your help in advance!

Colter

RobertJones6

Python does allow for <null> check in field calculator.
Open field calculator, choose the Python Parser.
Check the "Show Codeblock" box
Enter the following in the "Pre-Logic Script Code:" box

def Concatenate(field1,field2):
  if field2 == "":
    return field1
  else:
    return field1 + '-' + field2

in the bottom box enter (change the stuff between the !'s to your actual field names):

Concatenate(str(!MyField1!), str(!MyField2!))

This works because the null values ( <null> ) are converted to empty strings before being sent to the custom "Concatenate" function build in the code block. More info can be found at this link

Additional options:
if both fields contain <null> values and/or you want to you want to retain said <null> values... this example code should help:

Parser: Python
PreLogic:

def myFunction(one,two):
  if one == "":   # check if first field is <null>
    if two == "": # check if both fields are <null> and returns <null>
      pass
    else:
      return two   # otherwise, just return the second field value
  else:                # check if the first field is populated...
    if two == "": # if second field is blank
      return one  # return just the first field
    else:             # if both fields are populated
      return one + "-" + two  # return a concatenation of the fields with a hyphen deliminator

Calculation box:

myFunction(str(!field1!), str(!field2!))