Customize/remove Django select box blank option

user_30642 0
Viewed 61706

I'm using Django 1.0.2. I've written a ModelForm backed by a Model. This model has a ForeignKey where blank=False. When Django generates HTML for this form it creates a select box with one option for each row in the table referenced by the ForeignKey. It also creates an option at the top of the list that has no value and displays as a series of dashes:

<option value="">---------</option>

What I'd like to know is:

  1. What is the cleanest way to remove this auto-generated option from the select box?

  2. What is the cleanest way to customize it so that it shows as:

    <option value="">Select Item</option>

In searching for a solution I came across Django ticket 4653 which gave me the impression that others had the same question and that the default behavior of Django may have been modified. This ticket is over a year old so I was hoping there might be a cleaner way to accomplish these things.

Thanks for any help,

Jeff

Edit: I've configured the ForeignKey field as such: 

verb = models.ForeignKey(Verb, blank=False, default=get_default_verb)

This does set the default so that it's no longer the empty/dashes option but unfortunately it doesn't seem to resolve either of my questions. That is, the empty/dashes option still appears in the list.

django-forms django-models django python
15 Answers

Haven't tested this, but based on reading Django's code here and here I believe it should work:

class ThingForm(forms.ModelForm):
  class Meta:
    model = Thing
  
  def __init__(self, *args, **kwargs):
    super(ThingForm, self).__init__(*args, **kwargs)
    self.fields['verb'].empty_label = None

EDIT: This is documented, though you wouldn't necessarily know to look for ModelChoiceField if you're working with an auto-generated ModelForm.

EDIT: As jlpp notes in his answer, this isn't complete - you have to re-assign the choices to the widgets after changing the empty_label attribute. Since that's a bit hacky, the other option that might be easier to understand is just overriding the entire ModelChoiceField:

class ThingForm(forms.ModelForm):
  verb = ModelChoiceField(Verb.objects.all(), empty_label=None)

  class Meta:
    model = Thing
Carl_Meyer_32070

from the docs

The blank choice will not be included if the model field has blank=False and an explicit default value (the default value will be initially selected instead).

so set the default and you're ok

JZ_557240

With Carl's answer as a guide and after rooting around the Django source for a couple hours I think this is the complete solution:

  1. To remove the empty option (extending Carl's example):

    class ThingForm(models.ModelForm):
  class Meta:
    model = Thing

  def __init__(self, *args, **kwargs):
    super(ThingForm, self).__init__(*args, **kwargs)
    self.fields['verb'].empty_label = None
    # following line needed to refresh widget copy of choice list
    self.fields['verb'].widget.choices =
      self.fields['verb'].choices

  2. To customize the empty option label is essentially the same:

    class ThingForm(models.ModelForm):
  class Meta:
    model = Thing

  def __init__(self, *args, **kwargs):
    super(ThingForm, self).__init__(*args, **kwargs)
    self.fields['verb'].empty_label = "Select a Verb"
    # following line needed to refresh widget copy of choice list
    self.fields['verb'].widget.choices =
      self.fields['verb'].choices

I think this approach applies to all scenarios where ModelChoiceFields are rendered as HTML but I'm not positive. I found that when these fields are initialized, their choices are passed to the Select widget (see django.forms.fields.ChoiceField._set_choices). Setting the empty_label after initialization does not refresh the Select widget's list of choices. I'm not familiar enough with Django to know if this should be considered a bug.

user_306420

For a ForeignKey field, setting the default value to '' on the model will remove the blank option.

verb = models.ForeignKey(Verb, on_delete=models.CASCADE, default='')

For other fields like CharField you could set the default to None, but this does not work for ForeignKey fields in Django 1.11.

user_25320700

Since Django 1.7, you can customize the label for the blank value by adding a value to your choices list in your model field definition. From the documentation on configuring field choices:

Unless blank=False is set on the field along with a default then a label containing "---------" will be rendered with the select box. To override this behavior, add a tuple to choices containing None; e.g. (None, 'Your String For Display'). Alternatively, you can use an empty string instead of None where this makes sense - such as on a CharField.

I checked the documentation for different versions of Django and found that this was added in Django 1.7.

user_97062170

This becomes more complicated when the choices are foreign keys and if you want to filter the choices based on some criteria. In such case if you set the empty_label and then re-assign the choices (you can apply filtration here too) the empty label will be blank:

class ThingForm(models.ModelForm):

    class Meta:
    model = Thing

    def __init__(self, *args, **kwargs):
        super(ThingForm, self).__init__(*args, **kwargs)
        self.fields['verb'].empty_label = None
        self.fields['verb'].queryset=Verb.objects.all()

bbasically, the first line under init can be applied for all of the fields in the form with a loop or inline loop:

def __init__(self,user, *args, **kwargs):
    super(NewTicket, self).__init__(*args, **kwargs)
    for f in self.fields:
       self.fields[f].empty_label = None # or "Please Select" etc
user_61473740
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