sa125 sa125 - 5 months ago 42
Python Question

Flask - how do I combine Flask-WTF and Flask-SQLAlchemy to edit db models?

I'm trying to create an edit page for an existing model (already saved to db). The form object expects a multidict instance to populate its fields. This is what I have:

# the model - assumes Flask-SQLAlchemy
from flask.ext.sqlalchemy import SQLAlchemy
db = SQLAlchemy(app)
class Person(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(80), unique=True)

def __init__(self, name=name): = name

# the form - assumes Flask-WTF ext.
from import Form, TextField, Required, BooleanField

class PersonForm(Form):
name = TextField('name')

## the view
@app.route('/person/edit/<id>/', methods=['GET', 'POST'])
def edit_person(id):
person = Person.query.get(id)
if person:
form = PersonForm(person) #<-- raises error
return render_template('edit_person.html', form=form)

I could assign each field in the form to each field of the model
(['name'] =, etc...)
, but that seems redundant for large models. Is there any shortcut I'm missing?


Please refer to the wtforms documentation:

You pass in the "obj" as argument. This will bind the model properties to the form fields to provide the default values:

@app.route('/person/edit/<id>/', methods=['GET', 'POST'])
def edit_person(id):
    person = Person.query.get_or_404(id)
    form = PersonForm(obj=person)
    if form.validate_on_submit():

Notice also the "populate_obj" method. This is a handy shortcut which will bind the form values to the model properties (only those fields you have defined in your form, so quite safe to use).