How to model multilingual objects in Python using webapp2

Question

I build a multilingual web app using Python and webapp2.

I have an object called Tag, which has translations to multiple languages. For this reason, I have created the following models:

class Language(ndb.Model):
    code = ndb.StringProperty()
    name = ndb.StringProperty(indexed=False)


class MultilingualText(ndb.Model):
    language = ndb.KeyProperty(kind=Language)
    text = ndb.TextProperty(indexed=False)


class Tag(ndb.Model):
    translations = ndb.StructuredProperty(MultilingualText, repeated=True, indexed=False)

I would like to ask if this is the correct way to do such task, and how this structure can be used along with WTForms for validation, etc.

Thanks a lot in advance!

Answer 1

I think the best implementation can change depending on your goal and my answer here may not fulfill your needs.

For Language class, I would rather not use datastore for this purpose. I would use babel.Locale for determining display names.

As Tim said in the comment, I prefer using language code as the entity key. Here is an example Tag implementation, assuming every Tag needs a urlsafe slug.

def get_urlsafe_slug_from_tag(tag_text):
    # ...
    # ...

class Slug(ndb.Model):
    # use urlsafe slug as the key_name
    # You can optionally use the property bellow.
    available_translations = ndb.StringProperty(repeated=True)

class Tag(ndb.Model):
    # use language code as the key_name
    text = ndb.TextProperty()

When a tag is newly created, I will create two entities; a Slug entity with a unique urlsafe string (slug) for that tag as the key, as well as a Tag entity with the language code as the key and this Slug entity as its parent.

In this example, there is a property named available_translations, which will allow you to negotiate with the users language choices, and even execute a query which will return Slugs with a translation for a specified language (e.g. list Slugs with Japanese translation).

For WTForm validation, can you tell me how you want to validate the post data? I think you will be able to get better answer if you share your detailed needs.