exception

Traceback (most recent call last):
  File "metrics.py", line 32, in <module>
    test()
  File "metrics.py", line 27, in test
    distance_type='jaccard')
  File "/Users/ai/.virtualenvs/unshred/lib/python2.7/site-packages/mongoengine/queryset/base.py", line 201, in create
    return self._document(**kwargs).save()
  File "/Users/ai/.virtualenvs/unshred/lib/python2.7/site-packages/mongoengine/document.py", line 241, in save
    object_id = collection.save(doc, **write_concern)
  File "/Users/ai/.virtualenvs/unshred/lib/python2.7/site-packages/pymongo/collection.py", line 266, in save
    return self.insert(to_save, manipulate, safe, check_keys, **kwargs)
  File "/Users/ai/.virtualenvs/unshred/lib/python2.7/site-packages/pymongo/collection.py", line 362, in insert
    self.database.connection)
bson.errors.InvalidDocument: Cannot encode object: <Shreds: 100>

metrics.py

from __future__ import division

from itertools import chain, combinations
# from string import lower
from app import db
from flask.ext.mongoengine import Document
from mongoengine import ListField, ReferenceField, StringField, FloatField
from models import Shreds

class ShredsDistances(Document):
    shreds_pair = ListField(ReferenceField(Shreds), default=[])
    distance_type = StringField(max_length=10, default='')
    distance = FloatField()


def jaccard_distance(shred_a, shred_b):
    """ http://en.wikipedia.org/wiki/Jaccard_index """
    tags_a = set(map(lambda _: unicode(_.lower()), chain(*[s['tags'] for s in shred_a.tags])))
    tags_b = set(map(lambda _: unicode(_.lower()), chain(*[s['tags'] for s in shred_b.tags])))
    return 1 - len(tags_a.intersection(tags_b)) / len(tags_a.union(tags_b))


def calculate_jaccard_distance_matrix(shreds):
    for shred_a, shred_b in combinations(shreds, 2):
        yield shred_a, shred_b, jaccard_distance(shred_a, shred_b)


def test():
    shreds = Shreds.objects.exclude("features", "contour")
    for a, b, d in calculate_jaccard_distance_matrix(shreds):
        ShredsDistances.objects.create(
            shreds_pair=[a, b],
            distance=d,
            distance_type='jaccard')


if __name__ == '__main__':
    # import ipdb; ipdb.set_trace()
    test()