CODEWITHSUNDEEP
djangodjango-forms
user984003
user984003

Reputation: 29589

Django forms: default value if user leaves field blank

On Django Forms, how do I specify a default value for a field if the user leaves it blank? Initial sets an initial value, but the user can delete this.

Upvotes: 11

Views: 9317

Answers (3)

Minji Song
Minji Song

Reputation: 91

WallyBay's answer works for me. (+adding my experience)

If you leave the form field empty, None value will be passed. you can check this by printing out from.cleaned_data().

But, in my case, None value wasn't replaced with the Model's default value.

I tested by creating objects in the shell('python manage.py shell') passing 1)None value and 2)empty parameter.

My Model: 

class Cart(models.Model):
    total_amount = models.DecimalField(decimal_places=2, max_digits=1000, default=1, blank=True, null=True)
    quantity = models.IntegerField(default=1, blank=True)
    note = models.CharField(max_length=300, default='nothing to mention')
    summery = models.TextField(blank=False, null=True)
    event_won = models.BooleanField(default=False)

My Form: 

class CartForm(forms.ModelForm):
    summery = forms.CharField() 
    total_amount = forms.DecimalField(required=False)
    quantity = forms.IntegerField(initial=20)
    note = forms.CharField(widget=forms.TextInput(attrs={"placeholder":"write a note"}))

    class Meta: 
        model = Cart 
        fields = [
            'summery',
            'total_amount',
            'quantity',
            'note'
        ]

1) create the object by passing None value. Cart.objects.create(total_amount=None)

Result: Default value didn't apply. The total_amount is Null(None).

2) create the object without passing any. Cart.objects.create()

Result: default value worked. total_amount is 1.

When I delete null=True option for the total_amount in the Model class, it gives me an error 'NOT NULL constraint failed'

Upvotes: 0

WallyBay
WallyBay

Reputation: 156

If you're using a ModelForm simply follow Dan's advice.

If however you're simply using a Form then you may have to specify how to deal with validation. Example Documentation

class YourForm(forms.Form):
    ...

    def clean_field(self):
        data = self.cleaned_data['field']
        if not data:
            data = 'default value'

        return data

Upvotes: 13

Dan Hoerst
Dan Hoerst

Reputation: 6318

Set a default value in the model.

class YourModel(models.Model):
    this_field = models.TextField(default="default_value")

Upvotes: 6

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