Testing for empty fields

Question

Hello,
I have a Python script which flags records with inappropriate values.  Unfortunately, it is also flagging records without values.  I would like to know how I can check for the existence of a value in a field.  Normally, if there is a value in this field, it would be a string.  Here's what I have currently:if (suffval != '') and (suffval not in allowed):

the first condition is the one I'm having trouble with - the second condition seems to work fine.

I have also tried:if (suffval is not None)

and:if (not len(suffval))

Thanks so much for any guidance you can provide.

StacyRendall1 · Answer

Sweet, another handy one is isspace, which will pick up multiple spaces as well (your current code will only pick up one space). I.e.:if (not suffval.isspace()) and (suffval not in allowed):

LeighHolcombe · Answer

When your suggested code didn't work, I prayed something else was wrong.  Sure enough, instead of using NULLs or empty strings, my working database used a whitespace character.  The following code produced the intended results:if (suffval != ' ') and (suffval not in allowed)

(that's a space between the single quotes)

Thanks for your guidance, problem solved.

StacyRendall1 · Answer

Arc NULL is None in Python. Soif (suffval not in allowed) & (suffval is not None) & (len(suffval) != 0):
    # flag record

will flag records where the suffval is not allowed, not NULL (None) and not empty string.