Flask-WTF

WTF stands for WT Forms which is intended to provide the interactive user interface for the user. The WTF is a built-in module of the flask which provides an alternative way of designing forms in the flask web applications.

Why WTF Useful?

WTF is useful due to the following factors.

The form elements are sent along with the request object from the client side to the server side. Server-Side script needs to recreate the form elements since there is no direct mapping between the client side form elements and the variables to be used at the server side.
There is no way to render the HTML form data at real time.

The WT Forms is a flexible, form rendering, and validation library used to provide the user interface.

Install Flask-WTF

To use the WT forms, we need to install the flask-wtf library which can be installed using pip installer.

The module contains a Form class which is considered as the parent class for all the form related operations.

The standard form fields are listed below.

SN	Form Field	Description
1	TextField	It is used to represent the text filed HTML form element.
2	BooleanField	It is used to represent the checkbox HTML form element.
3	DecimalField	It is used to represent the text field to display the numbers with decimals.
4	IntegerField	It is used to represent the text field to display the integer values.
5	RadioField	It is used to represent the radio button HTML form element.
6	SelectField	It is used to represent the select form element.
7	TextAreaField	It is used to represent text area form element.
8	PasswordField	It is used to take the password as the form input from the user.
9	SubmitField	It provides represents the <input type = ‘submit’ value = ‘Submit’> html form element.

Consider the following example.

Example

In this example, we will create a form using flask WTF module. First, we will create a form class named as forms.py and we will import those form elements into the module formexample.py.

forms.py

  from flask_wtf import Form  from wtforms import TextField, IntegerField, TextAreaField, SubmitField, RadioField, SelectField  from wtforms import validators, ValidationError    class ContactForm(Form):     name = TextField(“Candidate Name “,[validators.Required(“Please enter your name.”)])     Gender = RadioField(‘Gender’, choices = [(‘M’,’Male’),(‘F’,’Female’)])     Address = TextAreaField(“Address”)          email = TextField(“Email”,[validators.Required(“Please enter your email address.”),     validators.Email(“Please enter your email address.”)])          Age = IntegerField(“Age”)     language = SelectField(‘Programming Languages’, choices = [(‘java’, ‘Java’),(‘py’, ‘Python’)])       submit = SubmitField(“Submit”)  

formexample.py

  from flask import Flask, render_template, request, flash  from forms import ContactForm  app = Flask(__name__)  app.secret_key = ‘development key’    @app.route(‘/contact’, methods = [‘GET’, ‘POST’])  def contact():     form = ContactForm()     if form.validate() == False:        flash(‘All fields are required.’)     return render_template(‘contact.html’, form = form)        @app.route(‘/success’,methods = [‘GET’,’POST’])  def success():     return render_template(“success.html”)    if __name__ == ‘__main__’:     app.run(debug = True)  

contact.html

  <!doctype html>  <html>     <body>        <h2 style = “text-align: center;”>Registration Form</h2>          {% for message in form.name.errors %}           <div>{{ message }}</div>        {% endfor %}                {% for message in form.email.errors %}           <div>{{ message }}</div>        {% endfor %}                <form action = “http://localhost:5000/success” method = “POST”>                         {{ form.hidden_tag() }}                            <div style = “font-size:18px;” font-weight:bold; margin-left:150px;>                 {{ form.name.label }}<br>                 {{ form.name }}                 <br>                 {{ form.Gender.label }} {{ form.Gender }}                 {{ form.Address.label }}<br>                 {{ form.Address }}                 <br>                 {{ form.email.label }}<br>                 {{ form.email }}                 <br>                 {{ form.Age.label }}<br>                 {{ form.Age }}                 <br>                 {{ form.language.label}}<br><br>                 {{ form.language }}                 <br><br>                 {{ form.submit }}              </div>                         </fieldset>        </form>     </body>  </html>  

Success.html

  <!DOCTYPE html>  <html>  <head>  <title></title>  </head>  <body>  <h1>Form posted successfully</h1>  </body>  </html>  

Output:

Flask-WTF

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