Forms

WORK IN PROGRESS

Just know that py4web.utils.form.Form is a pretty much equivalent to web2py’s SQLFORM.

The Form constructor accepts the following arguments:

Form(self,
     table,
     record=None,
     readonly=False,
     deletable=True,
     formstyle=FormStyleDefault,
     dbio=True,
     keep_values=False,
     form_name=False,
     hidden=None,
     before_validate=None):

Where:

• table: a DAL table or a list of fields (equivalent to old SQLFORM.factory)

• record: a DAL record or record id

• readonly: set to True to make a readonly form

• deletable: set to False to disallow deletion of record

• formstyle: a function that renders the form using helpers (FormStyleDefault)

• dbio: set to False to prevent any DB writes

• keep_values: if set to true, it remembers the values of the previously submitted form

• form_name: the optional name of this form

• hidden: a dictionary of hidden fields that is added to the form

• before_validate: an optional validator.

Example

Here is a simple example of a custom form not using database access. We declare an endpoint /form_example, which will be used both for the GET and for the POST of the form:

from py4web import Session, redirect, URL
from py4web.utils.dbstore import DBStore
from py4web.utils.form import Form, FormStyleBulma

db = DAL('sqlite:memory')
session =  Session(storage=DBStore(db))

@action('form_example', method=['GET', 'POST'])
@action.uses('form_example.html', session)
def form_example():
    form = Form([
        Field('product_name'),
        Field('product_quantity', 'integer')],
        formstyle=FormStyleBulma)
    if form.accepted:
        # Do something with form.vars['product_name'] and form.vars['product_quantity']
        redirect(URL('index'))
    return dict(form=form)

The form can be displayed in the template simply using [[=form]].

Form validation

The validation of form input can be done in two ways. One can define requires attributes of Field, or one can define explicitly a validation function. To do the latter, we pass to validate a function that takes the form and returns a dictionary, mapping field names to errors. If the dictionary is non-empty, the errors will be displayed to the user, and no database I/O will take place.

Here is an example:

from py4web import Field
from py4web.utils.form import Form, FormStyleBulma
from pydal.validators import IS_INT_IN_RANGE

def check_nonnegative_quantity(form):
    if not form.errors and form.vars['product_quantity'] % 2:
        form.errors['product_quantity'] = T('The product quantity must be even')

@action('form_example', method=['GET', 'POST'])
@action.uses('form_example.html', session)
def form_example():
    form = Form([
        Field('product_name'),
        Field('product_quantity', 'integer', requires=IS_INT_IN_RANGE(0,100))],
        validation=check_nonnegative_quantity,
        formstyle=FormStyleBulma)
    if form.accepted:
        # Do something with form.vars['product_name'] and form.vars['product_quantity']
        redirect(URL('index'))
    return dict(form=form)