forms.py

# external imports
from flask_wtf import FlaskForm
from wtforms import StringField, SelectField, SubmitField
from wtforms.validators import DataRequired, Length, NumberRange


class AddDeviceForm(FlaskForm):
    device_id = StringField('Device ID', 
                           validators=[DataRequired(), Length(min=5)])
    device_type = StringField('Device Type', 
                           validators=[DataRequired(), Length(min=5)])
    operational_status = SelectField('Operational Status',
                           choices=[(-1, 'Select...'), (0, 'Undefined'), (1, 'Disabled'), (2, 'Enabled')],
                           coerce=int,
                           validators=[DataRequired(), NumberRange(min=0)])
    submit = SubmitField('Add')