Yet Another Document Mapper

It’s small and simple ODM for use with MongoDB.


YAMD support MongoDB version 3.x only. MongoDB 2.x is not supported.

Minimal version of python is 3.5.

Quick start

Create the models

from datetime import datetime

import pymongo

from yadm import Database
from yadm import Document, EmbeddedDocument
from yadm import fields
from yadm.serialize import to_mongo

class User(Document):
    __collection__ = 'users'

    name = fields.StringField()
    email = fields.EmailField()

class PostLogItem(EmbeddedDocument):
    op = fields.StringField(choices=['created', 'comment_added'])
    at = fields.DatetimeField()
    data = fields.MongoMapField()

class Post(Document):
    __collection__ = 'posts'

    user = fields.ReferenceField(User)
    created_at = fields.DatetimeField(auto_now=True)
    title = fields.StringField()
    body = fields.StringField()
    log = fields.ListField(fields.EmbeddedDocumentField(PostLogItem))

class Comment(Document):
    __collection__ = 'comments'

    user = fields.ReferenceField(User)
    created_at = fields.DatetimeField(auto_now=True)
    post = fields.ReferenceField(Post)
    text = fields.StringField()

All documents creates from class Document. You can use multiple inheritance.

__collection__ magic attribute setups the collection name for documents of model.

Connect to database

client = pymongo.MongoClient('mongodb://localhost:27017')
db = Database(client, 'blog')

Database object is a wrapper about pymongo or motor Database.

Create documents


user = User(name='Bill', email='bill@galactic.hero')

Just insert document to database.


post = Post()
post.user = user
post.title = 'Small post'
post.body = 'Bla-bla-bla...'
post.log = [PostLogItem(op='created', at=datetime.utcnow())]

You can fill documents as above.

Comment the post

comment = Comment()
comment.user = user = post
comment.text = "RE: Bla-bla-bla..."
db.update_one(post, push={
    'log': to_mongo(PostLogItem(op='comment_added',

We add log item to post’s log. This is very usefull case.



qs = db(Post).find({'title': {'$regex': '^S'}})
assert qs.count() > 0
  1. db(Post) creates the QuerySet object;
  2. find method get the raw-query and return new QuerySet object with updated criteria;
  3. count method make the query to database and return value.
for post in qs:
    assert post.title.startswith('S')

__iter__ method make the find-query and returns the generator of documents.


post = db(Post).find_one({'user':})

find_one get the first finded document.

user = post.user

Get attribute with reference makes the query to referred collection. Warning: N+1 problem! We have a cache in QuerySet object and get one referred document only once for one queryset.


Yes! We have a joins! In userspace…

comments = db(Comment).find({'post':}).sort(('created_at', 1))
for comment in comments.join('user'):
    print(, comment.text)
  1. Create the queryset for comments;
  2. In join we get all documents for qs, get all users with one $in-query and bind to documents.


agg = (db.aggregate(Comment)
       .group(_id='post', count={'$sum': 1})

for item in agg:


1.5.0 (2017-12-31)

  • Experimental asyncio support;
  • Add ReferencesListField
    for lists of references.

1.4.15 (2017-12-27)

  • Add projection argument to get_document
    and reload;
  • Add Document.__default_projection__ attribute.

1.4.14 (2017-11-06)

  • Add EnumField
    for save enum.Enum;
  • Add EnumStateField
    for simple state machines based on enum.Enum.

1.4.13 (2017-10-31)

  • Add QuerySet.batch_size
    method for setup batch size for cursor;
  • Some minor fixes.

1.4.10 (2017-07-07)

1.4.9 (2017-07-06)

  • Add QuerySet.read_primary method
    for simple setup pymongo.read_preference.Primary.

1.4.4 (2017-05-17)

class Doc(Document):
    embedded = SimpleEmbeddedDocumentField({
        'i': IntegerField(),
        's': StringField(),

1.4.3 (2017-05-14)

1.4.2 (2017-04-09)

  • Additional arguments (like write_concern) for write operations;
  • create_fake save the documents with write concern “majority” by default.

1.4.0 (2017-04-05)

  • Drop pymongo 2 support;
  • Additional options for databases and collections;
  • Add Database.get_document;
  • Add TypedEmbeddedDocumentField;
  • reload argument of Database.update_one <yadm.database.Database.update_one>
    must be keyword (may be backward incompotable).

1.3.1 (2017-02-21)

  • Change raw data for Money;

1.3.0 (2017-02-19)

  • Add currency support to Money:
    • Totaly rewrite Money type. Now it is not subclass of Decimal;
    • Add storage for currencies:;

1.2.1 (2017-01-19)

1.2.0 (2016-12-27)

  • Drop MongoDB 2.X support;
  • Objects for update and remove results;
  • Use Faker instead fake-factory;

1.1.4 (2016-08-20)

1.1.3 (2016-07-23)

  • Add QuerySet.ids
    method for get only documents id’s from queryset;
  • Add Money.total_cents
    method and Money.total_cents classmethod;

1.1 (2016-04-26)

1.0 (2015-11-14)