Demonstrating the convert -> validate -> primitive structure

custom_schematics_type.py

#!/bin/env python2.7

from schematics.models import Model
from schematics.types import StringType
from schematics.exceptions import ValidationError


class EventType(StringType):
    DIVIDER = ':'
    
    def convert(self, value):
        if not isinstance(value, tuple):
            value = super(EventType, self).convert(value)
            value = value.split(self.DIVIDER)
        return tuple(str(v) for v in value)
        
    def validate_event(self, value, *a, **kw):
        if len(value) != 2:
            raise ValidationError('Not a valid Event ID: {}'.format(value))
        
    def to_primitive(self, value):
        return self.DIVIDER.join(value)


class Event(Model):
    id = EventType(required=True)


if __name__ == '__main__':
    
    # initialize from string
    event = Event({'id': '00:1001'})
    event.validate()
    print event.serialize()
    
    # set id from tuple
    event.id = (1,2)
    event.validate()
    print event.serialize()
    
    # invalid string
    try:
        event.id = 'hello'
        event.validate()
    except ValidationError as error:
        print error.message
        
    # invalid tuple
    try:
        event.id = (1,2,3)
        event.validate()
    except ValidationError as error:
        print error.message

output:

{'id': '00:1001'}
{'id': '1:2'}
{'id': ["Not a valid Event ID: ('hello',)"]}
{'id': ["Not a valid Event ID: ('1', '2', '3')"]}