Conditional field calculator expression

Question

I need to calculate the PIPEID field to equal the G_KEY_COMP field if PIPEID is null or PIPEID and G_KEY_COMP do not match. I think the first condition of the PIPEID being null is covered by the second condition of the fields not matching? I'm a novice on this topic and can't get the syntax I have to work. Here's what I've piecemealed together:

Pre-Logic Script Code:

def update(PIPEID,G_KEY_COMP):
 if PIPEID != G_KEY_COMP
  return G_KEY_COMP
else:
 return PIPEID

PIPEID = update(!PIPEID!, !G_KEY_COMP!)

I'm posting a screenshot of the field calculator window since I'm not able to get the indentation right in the codeblock.

Answer 1

Your code needs to be:

def update(PIPEID,G_KEY_COMP):
  if PIPEID is None:
    # PIPEID is NULL
    return G_KEY_COMP
  if PIPEID != G_KEY_COMP:
    # PIPEID has a different value to G_KEY_COMP
    return G_KEY_COMP
  else:
    return PIPEID

Answer 2

Pythonic inline if is working in Field Calculator expression

res=(on_false, on_true)[condition]

arcpy.CalculateField_management("fc" , "field" ,"(!PIPEID!, !G_KEY_COMP!)[!PIPEID! != !G_KEY_COMP!]" , "PYTHON_9.3")