Creating flask form with selects from more than one table - python-2.7

Question

I have seen a large number of tutorials that show login forms with flask and flash-wtf but none where multiple select boxes are populated from database table values.
This is what I am trying to do:
A simple registration form:
First name
Last name
Address Line 1
Address Line 2
City
State Id (populated from states library query of Id,state)
Country Id (populated from countries library query of country, id)
Sample code or a link to a walk through would be greatly appreciated.

Answer 1

I tried to find a explanation for how to do this and couldn't find one. So I'm going to write one here. This is how I do things, there's probably better ways to go about it.
Source Code
You can download the full source code for this tutorial on my github account. I'm pretty much copying and pasting from the source code, but just in case github dies some day here we go.
Configuration
Need to configure our application and the database connection. In most cases
you probably want to load all of this from a configuration file.
In this tutorial we're just going to use a basic sqlalchemy test database.
app = Flask(__name__)
app.config['SECRET_KEY'] = 'Insert_random_string_here'
Set this configuration to True if you want to see all of the SQL generated.
app.config['SQLALCHEMY_ECHO'] = False
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'
WTForms configuration strings
app.config['WTF_CSRF_ENABLED'] = True
CSRF tokens are important. Read more about them here,
https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)_Prevention_Cheat_Sheet
app.config['WTF_CSRF_SECRET_KEY'] = 'Insert_random_string_here'
db = SQLAlchemy(app)
SQLALchemy Model
Next we need to create our model classes that will be used during the creation
of the database and also when we want to manipulate the database. This should
normally be it's own seperate file.
I'm importanting from here as if this was it's own seperate file.
Normally you'd have to import doing something like
from application import db
class RegisteredUser(db.Model):
"""
loads and pushes registered user data after they have signed up.
SQLalchemy ORM table object which is used to load, and push, data from the
server memory scope to, and from, the database scope.
"""
__tablename__ = "RegisteredUser"
#all of the columns in the database.
registered_id = db.Column(db.Integer, primary_key=True)
first_name = db.Column(db.String(70))
last_name = db.Column(db.String(70))
address_line_one = db.Column(db.String(256))
address_line_two = db.Column(db.String(256))
city = db.Column(db.String(50))
"""
Now we're going to create all of the foreign keys for the RegisteredUser
table. The db.relationship section allows us to easily and automatically
join the other tables with registeredUser. The Join will only take place
if you attempt to access columns from the State or country table.
For more on Foreign keys using SQLAlchemy go to
"""
state_id = db.Column(
db.Integer,
db.ForeignKey('State.state_id'),
nullable=False)
#retrives the users name for display purposes.
state_by = db.relationship(
'State',
foreign_keys=[state_id],
backref=db.backref('State', lazy='dynamic'))
country_id = db.Column(
db.Integer,
db.ForeignKey('Country.country_id'),
nullable=False)
#retrives the users name for display purposes.
country_by = db.relationship(
'Country',
foreign_keys=[country_id],)
#this is the method and function style I've chosen when lines are too long
def __init__(
self,
first_name,
last_name,
address_line_one,
address_line_two,
city,
state_id,
country_id):
"""
Used to create a RegisteredUser object in the python server scope
We will be calling these init functions every time we use
RegisteredUser() as a 'function' call. It will create a SQLalchemy ORM
object for us.
"""
self.first_name = first_name
self.last_name = last_name
self.address_line_one = address_line_one
self.address_line_two = address_line_two
self.city = city
self.state_id = state_id
self.country_id = country_id
class State(db.Model): # pylint: disable-msg=R0903
"""
Holds State names for the database to load during the registration page.
SQLalchemy ORM table object which is used to load, and push, data from the
server memory scope to, and from, the database scope.
"""
__tablename__ = "State"
state_id = db.Column(db.Integer, primary_key=True)
state_name = db.Column(db.String(10), unique=True)
def __init__(self, state_name):
"""
Used to create a State object in the python server scope
"""
self.state_name = state_name
class Country(db.Model): # pylint: disable-msg=R0903
"""
Holds Country names for the database to load during the registration page.
SQLalchemy ORM table object which is used to load, and push, data from the
server memory scope to, and from, the database scope.
"""
__tablename__ = "Country"
country_id = db.Column(db.Integer, primary_key=True)
#longest country length is currently 163 letters
country_name = db.Column(db.String(256), unique=True)
def __init__(self, country_name):
"""
Used to create a Country object in the python server scope
"""
self.country_name = country_name
def create_example_data():
"""
Generates all of the demo data to be used later in the tutorial. This is
how we can use our ORM objects to push data to the database.
NOTE: create_example_data is called at the very bottom of the file.
"""
#Create a bunch of state models and add them to the current session.
#Note, this does not add rows to the database. We'll commit them later.
state_model = State(state_name="WA")
db.session.add(state_model)
state_model = State(state_name="AK")
db.session.add(state_model)
state_model = State(state_name="LA")
db.session.add(state_model)
#Normally I load this data from very large CVS or json files and run This
#sort of thing through a for loop.
country_model = Country("USA")
db.session.add(country_model)
country_model = Country("Some_Made_Up_Place")
db.session.add(country_model)
# Interesting Note: things will be commited in reverse order from when they
# were added.
try:
db.session.commit()
except IntegrityError as e:
print("attempted to push data to database. Not first run. continuing\
as normal")
WTForm
Now we're going to make our WTForms objects. These will have the data aquired
from the database placed on them, then we will pass them to our template files
where we will render them.
I'm importanting from here as if this was it's own seperate file.
import wtforms
import wtforms.validators as validators
from flask.ext.wtf import Form
class RegistrationForm(Form):
"""
This Form class contains all of the fileds that make up our registration
Form.
"""
#Get all of the text fields out of the way.
first_name_field = wtforms.TextField(
label="First Name",
validators=[validators.Length(max=70), validators.Required()])
last_name_field = wtforms.TextField(
label="Last Name",
validators=[validators.Length(max=70), validators.Required()])
address_line_one_field = wtforms.TextField(
label="Address",
validators=[validators.Length(max=256), validators.Required()])
address_line_two_field = wtforms.TextField(
label="Second Address",
validators=[validators.Length(max=256), ])
city_field = wtforms.TextField(
label="City",
validators=[validators.Length(max=50), validators.Required()])
# Now let's set all of our select fields.
state_select_field = wtforms.SelectField(label="State", coerce=int)
country_select_field = wtforms.SelectField(label="Country", coerce=int)
Views
import flask
def populate_form_choices(registration_form):
"""
Pulls choices from the database to populate our select fields.
"""
states = State.query.all()
countries = Country.query.all()
state_names = []
for state in states:
state_names.append(state.state_name)
#choices need to come in the form of a list comprised of enumerated lists
#example [('cpp', 'C++'), ('py', 'Python'), ('text', 'Plain Text')]
state_choices = list(enumerate(state_names))
country_names = []
for country in countries:
country_names.append(country.country_name)
country_choices = list(enumerate(country_names))
#now that we've built our choices, we need to set them.
registration_form.state_select_field.choices = state_choices
registration_form.country_select_field.choices = country_choices
#app.route('/', methods=['GET', 'POST'])
def demonstration():
"""
This will render a template that displays all of the form objects if it's
a Get request. If the use is attempting to Post then this view will push
the data to the database.
"""
#this parts a little hard to understand. flask-wtforms does an implicit
#call each time you create a form object. It attempts to see if there's a
#request.form object in this session and if there is it adds the data from
#the request to the form object.
registration_form = RegistrationForm()
#Before we attempt to validate our form data we have to set our select
#field choices. This is just something you need to do if you're going to
#use WTForms, even if it seems silly.
populate_form_choices(registration_form)
#This means that if we're not sending a post request then this if statement
#will always fail. So then we just move on to render the template normally.
if flask.request.method == 'POST' and registration_form.validate():
#If we're making a post request and we passed all the validators then
#create a registered user model and push that model to the database.
registered_user = RegisteredUser(
first_name=registration_form.data['first_name_field'],
last_name=registration_form.data['last_name_field'],
address_line_one=registration_form.data['address_line_one_field'],
address_line_two=registration_form.data['address_line_two_field'],
city=registration_form.data['city_field'],
state_id=registration_form.data['state_select_field'],
country_id=registration_form.data['country_select_field'],)
db.session.add(registered_user)
db.session.commit()
return flask.render_template(
template_name_or_list='success.html',
registration_form=registration_form,)
return flask.render_template(
template_name_or_list='registration.html',
registration_form=registration_form,)
runserver.py
Finally, this is for development purposes only. I normally have this in a
file called RunServer.py. For actually delivering your application you should
run behind a web server of some kind (Apache, Nginix, Heroku).
if __name__ == '__main__':
db.create_all()
create_example_data()
app.run(debug=True)
Templates
in macros.html
{% macro render_field(field) %}
<dt>{{ field.label }}
<dd>{{ field(**kwargs)|safe }}
{% if field.errors %}
<ul class=errors>
{% for error in field.errors %}
<li>{{ error }}</li>
{% endfor %}
</ul>
{% endif %}
</dd>
{% endmacro %}
{% macro render_data(field) %}
<dt>{{ field.label }}
<dd>{{ field.data|safe }}
{% if field.errors %}
<ul class=errors>
{% for error in field.errors %}
<li>{{ error }}</li>
{% endfor %}
</ul>
{% endif %}
</dd>
{% endmacro %}
In registration.html
{% from "macros.html" import render_field %}
<form method=post action="/">
{{registration_form.hidden_tag()}}
<dl>
{{ render_field(registration_form.first_name_field) }}
{{ render_field(registration_form.last_name_field) }}
{{ render_field(registration_form.address_line_one_field) }}
{{ render_field(registration_form.address_line_two_field) }}
{{ render_field(registration_form.city_field) }}
{{ render_field(registration_form.state_select_field) }}
{{ render_field(registration_form.country_select_field) }}
</dl>
<p><input type=submit value=Register>
</form>
Finally, in success.html
{% from "macros.html" import render_data %}
<h1> This data was saved to the database! </h1>
<form method=post action="/">
{{registration_form.hidden_tag()}}
<dl>
{{ render_data(registration_form.first_name_field) }}
{{ render_data(registration_form.last_name_field) }}
{{ render_data(registration_form.address_line_one_field) }}
{{ render_data(registration_form.address_line_two_field) }}
{{ render_data(registration_form.city_field) }}
{{ render_data(registration_form.state_select_field) }}
{{ render_data(registration_form.country_select_field) }}
</dl>
<p><input type=submit value=Register>
</form>