Flask-WTF - FlaskForm

[mateuszpozn]

Hi all
I am learning Flask and I have trouble understanding FlaskForm from Flask-WTF.
Code below.

hello.py

class NameForm(FlaskForm):
    name = StringField('What is your name?', validators=[DataRequired()])
    submit = SubmitField('Submit')

@app.route('/', methods=['GET', 'POST'])
def index():
    name = None
    form = NameForm()
    if form.validate_on_submit():
        name = form.name.data
    return render_template('index.html', form=form, name=name)

index.html

{% import "bootstrap/wtf.html" as wtf %}
{% block page_content %}
<div class="page-header">
    <h1>Hello, {% if name %}{{ name }}{% else %}Stranger{% endif %}!</h1>
</div>
{{ wtf.quick_form(form) }}
{% endblock %}

This simple application get name from the user and displays a personalized message. Suppose I have entered my name and click submit button. How it's possible that entered name is recived from form object (instance of NameForm) and send to render

name = form.name.data

when before this, new NameForm instance is assigned to the form variable?

form = NameForm()