I think you should reconsider your modelisation of data. You could define a new model representing the data that is on your json like for instance :

    class day(orm.Model):

    _name = 'horraire.day'

    _columns = {

        'day': fields.integer(...),

        'hours': fields.integer(...),

        'nature': fields.selection(...),

        'horraire_id': fields.many2one('other.object.you.use', ...)

    }

Now where you initially have your loop method you would do something like this, instead of your field horraire_data, you would have:

    'horraire_data': fields.one2many('horraire.day', 'horraire_id', ...)

And before and in your for loop, you would do :

    horraire_day_obj = self.pool.get('horraire.day')
    for :
        ... do your treatment ...
        
        horraire_day_obj.create(cr, uid, {
            'day': 1,
            'hours': 10,
            'nature': 'T',
            'horraire_id': ids[0] # your object_id
        }, context)
        
In this way your field 'horraire_data' will automatically link to all records 'horraire.day' attached to it.

Thanks  a lot for your answer but i want to know if it is possible to apply the

self.field_manager.set_values on a one2many field???