> On Thu, 28 Apr 2011 06:18:08 -0700, Brian Craft <bc...@thecraftstudio.com> wrote:
> > A form with a CharField seems to end up with a zero-length string in
> > the cleaned_data if the field is not in the form data. Is there any
> > good way to avoid this?
>
> Django docs say:
>
> "Note that empty string values will always get stored as empty strings,
> not as NULL. Only use null=True for non-string fields such as integers,
> booleans and dates. For both types of fields, you will also need to set
> blank=True if you wish to permit empty values in forms, as the null
> parameter only affects database storage (see blank).
>
> Avoid using null on string-based fields such as CharField and TextField
> unless you have an excellent reason. If a string-based field has
> null=True, that means it has two possible values for "no data": NULL,
> and the empty string. [...]
This is of course technically incorrect :-)
NULL means that you don't have any information, the empty string means
that you _know_ that the value is a string of length zero. This is
basic information theory.
Django is in good company though, most databases have problems round-
tripping one or more of the values NULL, "" (empty string), and " "
single space. What Django is doing is abstracting away inconsistent
database behavior -- and that's a good thing.
-- bjorn
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