RegexField – Django Forms

RegexField in Django Forms is a string field, for small- to large-sized strings which one can match with a particular regular expression. It is used for taking selected text inputs from the user. The default widget for this input is TextInput. It uses MaxLengthValidator and MinLengthValidator if max_length and min_length are provided. Otherwise, all inputs are valid.

RegexField has following optional arguments:

  • regex :- A regular expression specified either as a string or a compiled regular expression object.
  • max_length and min_length :- If provided, these arguments ensure that the string is at most or at least the given length.
  • strip :- If True (default), the value will be stripped of leading and trailing whitespace.

Syntax

field_name = forms.RegexField(**options)

Django form RegexField Explanation

Illustration of RegexField 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.

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from django import forms
  
# creating a form 
class GeeksForm(forms.Form):
    geeks_field = forms.RegexField(regex = "G.*s")

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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 URL. 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 = {}
    context['form'] = GeeksForm()
    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

django-forms-RegexField

Thus, an geeks_field RegexField is created by replacing “_” with ” “.

How to use RegexField ?

RegexField is used for input of small sized selected text in the database. One can input the Name of particular entity, Email, etc. Till now we have discussed how to implement RegexField 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,

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

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Now let’s try entering something else into the field.

django-forms-regexfield

Since it needs to be verified according to the regex provided which is input should start from ‘G’ and end with ‘s’. Let’s enter “GeeksForGeeks” in the field
1django-forms-regexfield
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. In above example we have the value in temp which we can use for any purpose.

django-forms-regexfields

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 RegexField 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 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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