topic Re: Testing for empty fields in Python Questions

Testing for empty fields

LeighHolcombe — Mon, 05 Sep 2011 21:48:05 GMT

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.

Re: Testing for empty fields

StacyRendall1 — Mon, 05 Sep 2011 22:04:10 GMT

By "records without values" do you mean records with NULL or records with just an empty string? If a string is empty it will have length zero.

I think this should do the trick:
"if not allowed and not none and not an empty string" (well, maybe you don't have to worry about the None, so you can delete that perhaps)

if (suffval not in allowed) & (suffval is not None) & (len(suffval) != 0):

Re: Testing for empty fields

LeighHolcombe — Mon, 05 Sep 2011 22:13:15 GMT

By "records without values" do you mean records with NULL or records with just an empty string? If a string is empty it will have length zero.

I assume the fields in question are NULL. I'm working with a street database, and this particular field is the directional suffix, which not every street requires.

Re: Testing for empty fields

StacyRendall1 — Sat, 11 Dec 2021 10:24:32 GMT

Arc NULL is None in Python. So

if (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.

Re: Testing for empty fields

LeighHolcombe — Tue, 06 Sep 2011 02:13:28 GMT

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.

Re: Testing for empty fields

StacyRendall1 — Tue, 06 Sep 2011 02:37:58 GMT

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):