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TypedChoiceField – Django Forms

  • Last Updated : 13 Feb, 2020

TypedChoiceField in Django Forms is a field just like ChoiceField, for selecting a particular choice out of a list of available choices. It is used to implement State, Countries etc. like fields for which information is already defined and user has to choose one. It is used for taking text inputs from the user. The default widget for this input is Select.It Normalizes to: A string. It is used to coerce a value to a particular data type.

TypedChoiceField has one extra required argument :

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  • choices :
    Either an iterable of 2-tuples to use as choices for this field, or a callable that returns such an iterable. This argument accepts the same formats as the choices argument to a model field.

TypedChoiceField has two optional arguments :



  • coerce :
    A function that takes one argument and returns a coerced value. Examples include the built-in int, float, bool and other types. Defaults to an identity function.
  • empty_value :
    The value to use to represent “empty.” Defaults to the empty string; None is another common choice here.

Syntax

field_name = forms.TypedChoiceField(**options)

Django form TypedChoiceField Explanation

Illustration of TypedChoiceField 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.




from django import forms
  
# iterable
GEEKS_CHOICES = (
    (1, "A"),
    (2, "B"),
    (3, "C"),
    (4, "D"),
    (5, "E"),
)
  
# creating a form 
class GeeksForm(forms.Form):
    geeks_field = forms.TypedChoiceField(
                   choices = GEEKS_CHOICES,
                   coerce = str
                  )

Add the geeks app to INSTALLED_APPS




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

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




from django.shortcuts import render
from .forms import GeeksForm
  
# Create your views here.
def home_view(request):
    context = {}
    context['form'] = GeeksForm()
    return render( request, "home.html", context)

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.




<form method = "GET">
    {{ form }}
    <input type = "submit" value = "Submit">
</form>

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






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

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

Python manage.py runserver

django-forms-typeschoicefield

Thus, an geeks_field TypedChoiceField is created by replacing “_” with ” “. It is a field to input choices of strings.

How to use TypedChoiceField ?

TypedChoiceField is used for input of small-sized strings in the database. One can input state, country, city, etc. Till now we have discussed how to implement TypedChoiceField but how to use it in the view for performing the logical part. To perform some logic we would need to get the value entered into field into a python string instance.
In views.py,




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

Now let’s try entering data into the field.

django-typechoicefield-forms

Now this data can be fetched using corresponding request dictionary. If method is GET, data would be available in request.GET and if post, request.POST correspondingly. we have used cleaned_data attribute of a form for fetching data from the view. In above example we have the value in temp which we can use for any purpose.

django-typedchoicefield-output-forms

It shows the int variable 2 as a string class as the value is coerced by TypedChoiceField. This is the advantage of ChoiceField over TypedChoiceField.

Core Field Arguments

Core Field arguments are the arguments given to each field for applying some constraint or imparting a particular characteristic to a particular Field. For example, adding an argument required = False to TypedChoiceField will enable it to be left blank by the user. Each Field class constructor takes at least these arguments. Some Field classes take additional, field-specific arguments, but the following should always be accepted:

Field OptionsDescription
requiredBy default, each Field class assumes the value is required, so to make it not required you need to set required=False
labelThe label argument lets you specify the “human-friendly” label for this field. This is used when the Field is displayed in a Form.
label_suffixThe label_suffix argument lets you override the form’s label_suffix on a per-field basis.
widgetThe widget argument lets you specify a Widget class to use when rendering this Field. See Widgets for more information.
help_textThe 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_messagesThe 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.
validatorsThe validators argument lets you provide a list of validation functions for this field.
localizeThe 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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