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Does having "Null" spelled out serve a function?

MattCotterill

I'm comparing two versions of a feature class one of which has <Null> spelled out in blank fields and the other just has blanks. Because of this difference, when I run the Detect Feature Changes tool, every feature shows up as having (at minimum) an attribute change. I want to want to run some python code to change either all <Null> to (blank) or vice versa so I can tell which features have been significantly changed. Is there an advantage to one or the other?

Thanks,
Matt

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danretired

A "blank" cell could be truly an empty string, or it could contain one space or more than one space or any of the non-printable utf characters. looking at the field wouldn't reveal what is what.

Also, numeric can't be represented by any nodata value, except for floats/decimal where there is NaN (not a number, but sadly, there isn't one for integers.

Spreadsheets have brought this empty cell evil to the world of GIS <NULL> is a good clue that the cell is not occupied.

All comments

danretired

And in my previous incarnation... there is this missive

The solution to <null> in tables - Esri Community

MattCotterill

Should I instead clear the <Null> values in the other feature class using your code?:

'' if !field! is None else !field!‍‍

JoshuaBixby

Don't do what you are planning on doing!

If you want the field to be NULL for records, then use Python None which is the Python mapping to SQL NULL. Writing out a text field with the same character representation that ArcGIS shows for SQL NULL will create massive confusion.

VinceAngelo

No, that wouldn't be wise, and it might not work -- What if the string field has a width of 5 or less?

You'd be better off reviewing the non-NULL empty fields for why they have corrupt values, rather than corrupting the valid NULLs.

- V

MattCotterill

Thanks, Dan!

It sounds like I should replace blank cells with <Null>. I noticed when I typed in <Null> in the title of this post, it would not show up until I changed the text to "Null". If I use the code below, will I run into problems because of the <> symbols?

'<Null>' if !field! is None else !field!‍‍

danretired

A "blank" cell could be truly an empty string, or it could contain one space or more than one space or any of the non-printable utf characters. looking at the field wouldn't reveal what is what.

Also, numeric can't be represented by any nodata value, except for floats/decimal where there is NaN (not a number, but sadly, there isn't one for integers.

Spreadsheets have brought this empty cell evil to the world of GIS <NULL> is a good clue that the cell is not occupied.

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