Populating Attribute field using Python code without copying over null rows?

Question

I am trying to copy the values from one column within my attribute table (!roomName!) over to another column (!spaceDiscriminator!). I understand how to do an easy field calc over for all the values but the problem is, I only want the rows in !roomName! that have values to copy over. If !roomName! contains a Null row then I do not want it copying over, instead I want the original value in !spaceDiscriminator! to remain and not get edited. I cannot figure out how to do this adequately. I have attached my code below:

In the first if statement I have tried many alternative scenarios. If x == None: seems to be the one that accurately selects the Null fields I don't want copying over. return None still edits the !spaceDiscriminator! field however. I've tried to use continue there but it throws and error. Is there any simple statement I can use there that basically says, "if the value is none/Null continue to the next row and leave original !spaceDiscriminator! value".

Answer 1

The code you seek would be something like this:

testme(!roomname!,!spaceddiscriminator!)

def testme(x,y):
  if x is None:
    return y
  else:
    return x

As you can see you can pass more than one field value into your function, in your case the value from the very field you are updating.

Answer 2

Just Select by Attributes where [RoomName] is not null, then do your simple calculation. Should only operate on selected rows.