initial – Django Form Field Validation

Built-in Form Field Validations in Django Forms are the default validations that come predefined to all fields. Every field comes in with some built-in validations from Django validators. Each Field class constructor takes some fixed arguments.

initial is used to change the value of the field in the input tag when rendering this Field in an unbound Form. initial accepts as input a string which is new value of field. The default initial for a Field is empty. Let’s check how to use initial in a field using a project.

Syntax



field_name = models.Field(option = value)

Django Form Field Validation initial Explanation

Illustration of initial using an Example. Consider a project named geeksforgeeks having an app named geeks.

Refer to the following articles to check how to create a project and an app in Django.

Enter the following code into forms.py file of geeks app. We will be using CharField for experimenting for all field options.

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from django import forms
  
class GeeksForm(forms.Form):
    geeks_field = forms.CharField(initial = "Enter your Name")

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Add the geeks app to INSTALLED_APPS

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# Application definition
  
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'geeks',
]

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Now to render this form into a view we need a view and a URL mapped to that view. Let’s create a view first in views.py of geeks app,

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from django.shortcuts import render
from .forms import GeeksForm
  
# Create your views here.
def home_view(request):
    context = {}
    form = GeeksForm(request.POST or None)
    context['form'] = form
    if request.POST:
        if form.is_valid():
            temp = form.cleaned_data.get("geeks_field")
            print(temp)
    return render(request, "home.html", context)

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Here we are importing that particular form from forms.py and creating an object of it in the view so that it can be rendered in a template.
Now, to initiate a Django form you need to create home.html where one would be designing the stuff as they like. Let’s create a form in home.html.

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<form method = "POST">
    {% csrf_token %}
    {{ form }}
    <input type = "submit" value = "Submit">
</form>

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Finally, a URL to map to this view in urls.py

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from django.urls import path
  
# importing views from views..py
from .views import home_view
  
URLpatterns = [
    path('', home_view ),
]

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Let’s run the server and check what has actually happened, Run

Python manage.py runserver

initial-–-Django-Form-Field-Validation

Thus, an geeks_field CharField is created with initial “Enter your Name”.

More Built-in Form Validations

Field Options Description
required By default, each Field class assumes the value is required, so to make it not required you need to set required=False
label The label argument lets you specify the “human-friendly” label for this field. This is used when the Field is displayed in a Form.
label_suffix The label_suffix argument lets you override the form’s label_suffix on a per-field basis.
widget The widget argument lets you specify a Widget class to use when rendering this Field. See Widgets for more information.
help_text The help_text argument lets you specify descriptive text for this Field. If you provide help_text, it will be displayed next to the Field when the Field is rendered by one of the convenience Form methods.
error_messages The error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override.
validators The validators argument lets you provide a list of validation functions for this field.
localize The localize argument enables the localization of form data input, as well as the rendered output.
disabled. The disabled boolean argument, when set to True, disables a form field using the disabled HTML attribute so that it won’t be editable by users.



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