How to test if a date is null

Question

I am writing a python script geoprocessing tool and need to use an UpdateCursor to populate a text field with either 'Y' or 'N' depending on whether a date field is null or not. Here is my code:

with arcpy.da.UpdateCursor(arcpy.env.scratchGDB + r"/cn42n_table", (cn42n_status_field_validated, cn42n_cancel_date_field_validated, "CANC", "PARC")) as cursor:
  for row in cursor:
       if "CANC" in row[0] or not row[1] is None:
            row[2] = "Y"
       else:
            row[2] = "N"

if "PARC" in row[0]:
            row[3] = "Y"
       else:
            row[3] = "N"

I have tried several ways of checking if row[1] (my date field) is not null but whatever I try the 'CANC' field is populated with a 'Y'.

Could someone please tell me the correct way to do this?

Thanks

Dan

DanEvans · Answer

Ah! The problem was that the field parameter I was passing to ValidateFieldName was the status field again, not the cancel field!

Thanks for the help anyway...

Dan

Zeke · Answer

Well, without going through everything, you could try testing if len(row[1]) < 1. You could also try printing row[1] in the loop. see what values it's finding. Or enclose row[1] is None in (), or even try Null instead of None, although I don't expect that to work.

If nothing else, these methods might give you some clue as to what's going on.

DanEvans · Answer

It's as if python is not recognising the nulls as None.

I have confirmed this by commenting out the first part so it's just:

if not row[1] is None:
     row[2] = "Y"
else:
     row[2] = "N"

And still the result is 'Y' for everything...

How do date fields come across into Python? Are they datetime objects? Whatever type python sees them as, could it be converting the nulls to some other value (January 1st 1970 or something?)

Dan