Blank option in required ChoiceField

I want my ChoiceField in ModelForm to have a blank option (------) but it's required.

I need to have blank option to prevent user from开发者_JAVA百科 accidentally skipping the field thus select the wrong option.

This works for at least 1.4 and later:

CHOICES = (
    ('', '-----------'),
    ('foo', 'Foo')
)

class FooForm(forms.Form):
    foo = forms.ChoiceField(choices=CHOICES)

Since ChoiceField is required (by default), it will complain about being empty when first choice is selected and wouldn't if second.

It's better to do it like this than the way Yuji Tomita showed, because this way you use Django's localized validation messages.

You could validate the field with clean_FOO

CHOICES = (
    ('------------','-----------'), # first field is invalid.
    ('Foo', 'Foo')
)
class FooForm(forms.Form):
    foo = forms.ChoiceField(choices=CHOICES)

    def clean_foo(self):
        data = self.cleaned_data.get('foo')
        if data == self.fields['foo'].choices[0][0]:
            raise forms.ValidationError('This field is required')
        return data

If it's a ModelChoiceField, you can supply the empty_label argument.

foo = forms.ModelChoiceField(queryset=Foo.objects.all(), 
                    empty_label="-------------")

This will keep the form required, and if ----- is selected, will throw a validation error.

You can also override form's __init__() method and modify the choices field attribute, reasigning a new list of tuples. (This may be useful for dynamic changes):

def __init__(self, *args, **kwargs):
    super(MyForm, self).__init__(*args, **kwargs)
    self.fields['my_field'].choices = [('', '---------')] + self.fields['my_field'].choices

in argument add null = True

like this

gender = models.CharField(max_length=1, null = True)

http://docs.djangoproject.com/en/dev/ref/models/fields/

for your comment

THEME_CHOICES = (
    ('--', '-----'),
    ('DR', 'Domain_registery'),
)
    theme = models.CharField(max_length=2, choices=THEME_CHOICES)