Question

I’ve a model like this:

class Message(models.Model):
    msg = models.CharField(max_length = 150)

and I have a form for insert the field. Actually django allows empty spaces, for examples if I inset in the field one space it works. But now I want to fix this: the field is not required, but if a user insert a spaces, the validation should fail.

I’ve added:

class Message(models.Model):
    msg = models.CharField(max_length = 150, blank = False)

but it doesn’t work.
What’s the mistake?

Answer 1

Whitespace is not considered to be blank. blank specifically refers to no input (i.e. an empty string ''). You will need to use a model field validator that raises an exception if the value only consists of spaces. See the documentation for details.

Example:

def validate_not_spaces(value):
    if isinstance(value, str) and value.strip() == '':
        raise ValidationError(u"You must provide more than just whitespace.")

class Message(models.Model):
    msg = models.CharField(max_length=150, blank=False,
                           validators=[validate_not_spaces])