3. API Reference

3.1. Connecting

mongoengine.connect(db, alias='default', **kwargs)

Connect to the database specified by the ‘db’ argument.

Connection settings may be provided here as well if the database is not running on the default port on localhost. If authentication is needed, provide username and password arguments as well.

Multiple databases are supported by using aliases. Provide a separate alias to connect to a different instance of mongod.

Changed in version 0.6: - added multiple database support.

mongoengine.register_connection(alias, name, host=None, port=None, is_slave=False, read_preference=False, slaves=None, username=None, password=None, **kwargs)

Add a connection.

Parameters:
  • alias – the name that will be used to refer to this connection throughout MongoEngine
  • name – the name of the specific database to use
  • host – the host name of the mongod instance to connect to
  • port – the port that the mongod instance is running on
  • is_slave – whether the connection can act as a slave ** Depreciated pymongo 2.0.1+
  • read_preference – The read preference for the collection ** Added pymongo 2.1
  • slaves – a list of aliases of slave connections; each of these must be a registered connection that has is_slave set to True
  • username – username to authenticate with
  • password – password to authenticate with
  • kwargs – allow ad-hoc parameters to be passed into the pymongo driver

3.2. Documents

class mongoengine.Document(*args, **values)

The base class used for defining the structure and properties of collections of documents stored in MongoDB. Inherit from this class, and add fields as class attributes to define a document’s structure. Individual documents may then be created by making instances of the Document subclass.

By default, the MongoDB collection used to store documents created using a Document subclass will be the name of the subclass converted to lowercase. A different collection may be specified by providing collection to the meta dictionary in the class definition.

A Document subclass may be itself subclassed, to create a specialised version of the document that will be stored in the same collection. To facilitate this behaviour a _cls field is added to documents (hidden though the MongoEngine interface). To disable this behaviour and remove the dependence on the presence of _cls set allow_inheritance to False in the meta dictionary.

A Document may use a Capped Collection by specifying max_documents and max_size in the meta dictionary. max_documents is the maximum number of documents that is allowed to be stored in the collection, and max_size is the maximum size of the collection in bytes. If max_size is not specified and max_documents is, max_size defaults to 10000000 bytes (10MB).

Indexes may be created by specifying indexes in the meta dictionary. The value should be a list of field names or tuples of field names. Index direction may be specified by prefixing the field names with a + or - sign.

Automatic index creation can be disabled by specifying attr:auto_create_index in the meta dictionary. If this is set to False then indexes will not be created by MongoEngine. This is useful in production systems where index creation is performed as part of a deployment system.

By default, _cls will be added to the start of every index (that doesn’t contain a list) if allow_inheritance is True. This can be disabled by either setting cls to False on the specific index or by setting index_cls to False on the meta dictionary for the document.

Initialise a document or embedded document

Parameters:
  • __auto_convert – Try and will cast python objects to Object types
  • values – A dictionary of values for the document
objects

A QuerySet object that is created lazily on access.

cascade_save(*args, **kwargs)

Recursively saves any references / generic references on an objects

classmethod compare_indexes()

Compares the indexes defined in MongoEngine with the ones existing in the database. Returns any missing/extra indexes.

delete(**write_concern)

Delete the Document from the database. This will only take effect if the document has been previously saved.

Parameters:write_concern – Extra keyword arguments are passed down which will be used as options for the resultant getLastError command. For example, save(..., write_concern={w: 2, fsync: True}, ...) will wait until at least two servers have recorded the write and will force an fsync on the primary server.
classmethod drop_collection()

Drops the entire collection associated with this Document type from the database.

classmethod ensure_index(key_or_list, drop_dups=False, background=False, **kwargs)

Ensure that the given indexes are in place.

Parameters:key_or_list – a single index key or a list of index keys (to construct a multi-field index); keys may be prefixed with a + or a - to determine the index ordering
classmethod ensure_indexes()

Checks the document meta data and ensures all the indexes exist.

Global defaults can be set in the meta - see Defining documents

Note

You can disable automatic index creation by setting auto_create_index to False in the documents meta data

classmethod list_indexes(go_up=True, go_down=True)

Lists all of the indexes that should be created for given collection. It includes all the indexes from super- and sub-classes.

my_metaclass

alias of TopLevelDocumentMetaclass

classmethod register_delete_rule(document_cls, field_name, rule)

This method registers the delete rules to apply when removing this object.

reload(max_depth=1)

Reloads all attributes from the database.

New in version 0.1.2.

Changed in version 0.6: Now chainable

save(force_insert=False, validate=True, clean=True, write_concern=None, cascade=None, cascade_kwargs=None, _refs=None, **kwargs)

Save the Document to the database. If the document already exists, it will be updated, otherwise it will be created.

Parameters:
  • force_insert – only try to create a new document, don’t allow updates of existing documents
  • validate – validates the document; set to False to skip.
  • clean – call the document clean method, requires validate to be True.
  • write_concern – Extra keyword arguments are passed down to save() OR insert() which will be used as options for the resultant getLastError command. For example, save(..., write_concern={w: 2, fsync: True}, ...) will wait until at least two servers have recorded the write and will force an fsync on the primary server.
  • cascade – Sets the flag for cascading saves. You can set a default by setting “cascade” in the document __meta__
  • cascade_kwargs – (optional) kwargs dictionary to be passed throw to cascading saves. Implies cascade=True.
  • _refs – A list of processed references used in cascading saves

Changed in version 0.5: In existing documents it only saves changed fields using set / unset. Saves are cascaded and any DBRef objects that have changes are saved as well.

Changed in version 0.6: Added cascading saves

Changed in version 0.8: Cascade saves are optional and default to False. If you want fine grain control then you can turn off using document meta[‘cascade’] = True. Also you can pass different kwargs to the cascade save using cascade_kwargs which overwrites the existing kwargs with custom values.

Handles dereferencing of DBRef objects to a maximum depth in order to cut down the number queries to mongodb.

New in version 0.5.

switch_collection(collection_name)

Temporarily switch the collection for a document instance.

Only really useful for archiving off data and calling save():

user = User.objects.get(id=user_id)
user.switch_collection('old-users')
user.save()

If you need to read from another database see switch_db

Parameters:collection_name – The database alias to use for saving the document
switch_db(db_alias)

Temporarily switch the database for a document instance.

Only really useful for archiving off data and calling save():

user = User.objects.get(id=user_id)
user.switch_db('archive-db')
user.save()

If you need to read from another database see switch_db

Parameters:db_alias – The database alias to use for saving the document
to_dbref()

Returns an instance of DBRef useful in __raw__ queries.

update(**kwargs)

Performs an update on the Document A convenience wrapper to update().

Raises OperationError if called on an object that has not yet been saved.

class mongoengine.EmbeddedDocument(*args, **kwargs)

A Document that isn’t stored in its own collection. EmbeddedDocuments should be used as fields on Documents through the EmbeddedDocumentField field type.

A EmbeddedDocument subclass may be itself subclassed, to create a specialised version of the embedded document that will be stored in the same collection. To facilitate this behaviour a _cls field is added to documents (hidden though the MongoEngine interface). To disable this behaviour and remove the dependence on the presence of _cls set allow_inheritance to False in the meta dictionary.

my_metaclass

alias of DocumentMetaclass

class mongoengine.DynamicDocument(*args, **values)

A Dynamic Document class allowing flexible, expandable and uncontrolled schemas. As a Document subclass, acts in the same way as an ordinary document but has expando style properties. Any data passed or set against the DynamicDocument that is not a field is automatically converted into a DynamicField and data can be attributed to that field.

Note

There is one caveat on Dynamic Documents: fields cannot start with _

Initialise a document or embedded document

Parameters:
  • __auto_convert – Try and will cast python objects to Object types
  • values – A dictionary of values for the document
my_metaclass

alias of TopLevelDocumentMetaclass

class mongoengine.DynamicEmbeddedDocument(*args, **kwargs)

A Dynamic Embedded Document class allowing flexible, expandable and uncontrolled schemas. See DynamicDocument for more information about dynamic documents.

my_metaclass

alias of DocumentMetaclass

class mongoengine.document.MapReduceDocument(document, collection, key, value)

A document returned from a map/reduce query.

Parameters:
  • collection – An instance of Collection
  • key – Document/result key, often an instance of ObjectId. If supplied as an ObjectId found in the given collection, the object can be accessed via the object property.
  • value – The result(s) for this key.

New in version 0.3.

object

Lazy-load the object referenced by self.key. self.key should be the primary_key.

class mongoengine.ValidationError(message='', **kwargs)

Validation exception.

May represent an error validating a field or a document containing fields with validation errors.

Variables:errors – A dictionary of errors for fields within this document or list, or None if the error is for an individual field.
to_dict()

Returns a dictionary of all errors within a document

Keys are field names or list indices and values are the validation error messages, or a nested dictionary of errors for an embedded document or list.

3.3. Context Managers

class mongoengine.context_managers.switch_db(cls, db_alias)

switch_db alias context manager.

Example

# Register connections
register_connection('default', 'mongoenginetest')
register_connection('testdb-1', 'mongoenginetest2')

class Group(Document):
    name = StringField()

Group(name="test").save()  # Saves in the default db

with switch_db(Group, 'testdb-1') as Group:
    Group(name="hello testdb!").save()  # Saves in testdb-1

Construct the switch_db context manager

Parameters:
  • cls – the class to change the registered db
  • db_alias – the name of the specific database to use
class mongoengine.context_managers.no_dereference(cls)

no_dereference context manager.

Turns off all dereferencing in Documents for the duration of the context manager:

with no_dereference(Group) as Group:
    Group.objects.find()

Construct the no_dereference context manager.

Parameters:cls – the class to turn dereferencing off on
class mongoengine.context_managers.query_counter

Query_counter context manager to get the number of queries.

Construct the query_counter.

3.4. Querying

class mongoengine.queryset.QuerySet(document, collection)

The default queryset, that builds queries and handles a set of results returned from a query.

Wraps a MongoDB cursor, providing Document objects as the results.

__call__(q_obj=None, class_check=True, slave_okay=False, read_preference=None, **query)

Filter the selected documents by calling the QuerySet with a query.

Parameters:
  • q_obj – a Q object to be used in the query; the QuerySet is filtered multiple times with different Q objects, only the last one will be used
  • class_check – If set to False bypass class name check when querying collection
  • slave_okay – if True, allows this query to be run against a replica secondary.
  • query – Django-style query keyword arguments
Params read_preference:
 

if set, overrides connection-level read_preference from ReplicaSetConnection.
all()

Returns all documents.

all_fields()

Include all fields. Reset all previously calls of .only() or .exclude().

post = BlogPost.objects.exclude("comments").all_fields()

New in version 0.5.

as_pymongo(coerce_types=False)

Instead of returning Document instances, return raw values from pymongo.

Parameters:coerce_type – Field types (if applicable) would be use to coerce types.
average(field)

Average over the values of the specified field.

Parameters:field – the field to average over; use dot-notation to refer to embedded document fields

Changed in version 0.5: - updated to map_reduce as db.eval doesnt work with sharding.

clone()
Creates a copy of the current
QuerySet

New in version 0.5.

clone_into(cls)

Creates a copy of the current BaseQuerySet into another child class

count(with_limit_and_skip=True)

Count the selected elements in the query.

Parameters:(optional) (with_limit_and_skip) – take any limit() or skip() that has been applied to this cursor into account when getting the count
create(**kwargs)

Create new object. Returns the saved object instance.

New in version 0.4.

delete(write_concern=None, _from_doc_delete=False)

Delete the documents matched by the query.

Parameters:
  • write_concern – Extra keyword arguments are passed down which will be used as options for the resultant getLastError command. For example, save(..., write_concern={w: 2, fsync: True}, ...) will wait until at least two servers have recorded the write and will force an fsync on the primary server.
  • _from_doc_delete – True when called from document delete therefore signals will have been triggered so don’t loop.
distinct(field)

Return a list of distinct values for a given field.

Parameters:field – the field to select distinct values from

Note

This is a command and won’t take ordering or limit into account.

New in version 0.4.

Changed in version 0.5: - Fixed handling references

Changed in version 0.6: - Improved db_field refrence handling

ensure_index(**kwargs)

Deprecated use Document.ensure_index()

exclude(*fields)

Opposite to .only(), exclude some document’s fields.

post = BlogPost.objects(...).exclude("comments")

Note

exclude() is chainable and will perform a union :: So with the following it will exclude both: title and author.name:

post = BlogPost.objects.exclude("title").exclude("author.name")

all_fields() will reset any field filters.

Parameters:fields – fields to exclude

New in version 0.5.

exec_js(code, *fields, **options)

Execute a Javascript function on the server. A list of fields may be provided, which will be translated to their correct names and supplied as the arguments to the function. A few extra variables are added to the function’s scope: collection, which is the name of the collection in use; query, which is an object representing the current query; and options, which is an object containing any options specified as keyword arguments.

As fields in MongoEngine may use different names in the database (set using the db_field keyword argument to a Field constructor), a mechanism exists for replacing MongoEngine field names with the database field names in Javascript code. When accessing a field, use square-bracket notation, and prefix the MongoEngine field name with a tilde (~).

Parameters:
  • code – a string of Javascript code to execute
  • fields – fields that you will be using in your function, which will be passed in to your function as arguments
  • options – options that you want available to the function (accessed in Javascript through the options object)
explain(format=False)

Return an explain plan record for the QuerySet‘s cursor.

Parameters:format – format the plan before returning it
fields(_only_called=False, **kwargs)

Manipulate how you load this document’s fields. Used by .only() and .exclude() to manipulate which fields to retrieve. Fields also allows for a greater level of control for example:

Retrieving a Subrange of Array Elements:

You can use the $slice operator to retrieve a subrange of elements in an array. For example to get the first 5 comments:

post = BlogPost.objects(...).fields(slice__comments=5)
Parameters:kwargs – A dictionary identifying what to include

New in version 0.5.

filter(*q_objs, **query)

An alias of __call__()

first()

Retrieve the first object matching the query.

from_json(json_data)

Converts json data to unsaved objects

get(*q_objs, **query)

Retrieve the the matching object raising MultipleObjectsReturned or DocumentName.MultipleObjectsReturned exception if multiple results and DoesNotExist or DocumentName.DoesNotExist if no results are found.

New in version 0.3.

get_or_create(write_concern=None, auto_save=True, *q_objs, **query)

Retrieve unique object or create, if it doesn’t exist. Returns a tuple of (object, created), where object is the retrieved or created object and created is a boolean specifying whether a new object was created. Raises MultipleObjectsReturned or DocumentName.MultipleObjectsReturned if multiple results are found. A new document will be created if the document doesn’t exists; a dictionary of default values for the new document may be provided as a keyword argument called defaults.

Note

This requires two separate operations and therefore a race condition exists. Because there are no transactions in mongoDB other approaches should be investigated, to ensure you don’t accidently duplicate data when using this method. This is now scheduled to be removed before 1.0

Parameters:
  • write_concern – optional extra keyword arguments used if we have to create a new document. Passes any write_concern onto save()
  • auto_save – if the object is to be saved automatically if not found.

Deprecated since version 0.8.

Changed in version 0.6: - added auto_save

New in version 0.3.

hint(index=None)

Added ‘hint’ support, telling Mongo the proper index to use for the query.

Judicious use of hints can greatly improve query performance. When doing a query on multiple fields (at least one of which is indexed) pass the indexed field as a hint to the query.

Hinting will not do anything if the corresponding index does not exist. The last hint applied to this cursor takes precedence over all others.

New in version 0.5.

in_bulk(object_ids)

Retrieve a set of documents by their ids.

Parameters:object_ids – a list or tuple of ObjectIds
Return type:dict of ObjectIds as keys and collection-specific Document subclasses as values.

New in version 0.3.

insert(doc_or_docs, load_bulk=True, write_concern=None)

bulk insert documents

Parameters:
  • docs_or_doc – a document or list of documents to be inserted
  • (optional) (load_bulk) – If True returns the list of document instances
  • write_concern – Extra keyword arguments are passed down to insert() which will be used as options for the resultant getLastError command. For example, insert(..., {w: 2, fsync: True}) will wait until at least two servers have recorded the write and will force an fsync on each server being written to.

By default returns document instances, set load_bulk to False to return just ObjectIds

New in version 0.5.

item_frequencies(field, normalize=False, map_reduce=True)

Returns a dictionary of all items present in a field across the whole queried set of documents, and their corresponding frequency. This is useful for generating tag clouds, or searching documents.

Note

Can only do direct simple mappings and cannot map across ReferenceField or GenericReferenceField for more complex counting a manual map reduce call would is required.

If the field is a ListField, the items within each list will be counted individually.

Parameters:
  • field – the field to use
  • normalize – normalize the results so they add to 1.0
  • map_reduce – Use map_reduce over exec_js

Changed in version 0.5: defaults to map_reduce and can handle embedded document lookups

limit(n)

Limit the number of returned documents to n. This may also be achieved using array-slicing syntax (e.g. User.objects[:5]).

Parameters:n – the maximum number of objects to return
map_reduce(map_f, reduce_f, output, finalize_f=None, limit=None, scope=None)

Perform a map/reduce query using the current query spec and ordering. While map_reduce respects QuerySet chaining, it must be the last call made, as it does not return a maleable QuerySet.

See the test_map_reduce() and test_map_advanced() tests in tests.queryset.QuerySetTest for usage examples.

Parameters:
  • map_f – map function, as Code or string
  • reduce_f – reduce function, as Code or string
  • output – output collection name, if set to ‘inline’ will try to use inline_map_reduce This can also be a dictionary containing output options see: http://docs.mongodb.org/manual/reference/command/mapReduce/#dbcmd.mapReduce
  • finalize_f – finalize function, an optional function that performs any post-reduction processing.
  • scope – values to insert into map/reduce global scope. Optional.
  • limit – number of objects from current query to provide to map/reduce method

Returns an iterator yielding MapReduceDocument.

Note

Map/Reduce changed in server version >= 1.7.4. The PyMongo map_reduce() helper requires PyMongo version >= 1.11.

Changed in version 0.5: - removed keep_temp keyword argument, which was only relevant for MongoDB server versions older than 1.7.4

New in version 0.3.

next()

Wrap the result in a Document object.

no_cache()

Convert to a non_caching queryset

New in version 0.8.3: Convert to non caching queryset

no_dereference()

Turn off any dereferencing for the results of this queryset.

no_sub_classes()

Only return instances of this document and not any inherited documents

none()

Helper that just returns a list

only(*fields)

Load only a subset of this document’s fields.

post = BlogPost.objects(...).only("title", "author.name")

Note

only() is chainable and will perform a union :: So with the following it will fetch both: title and author.name:

post = BlogPost.objects.only("title").only("author.name")

all_fields() will reset any field filters.

Parameters:fields – fields to include

New in version 0.3.

Changed in version 0.5: - Added subfield support

order_by(*keys)

Order the QuerySet by the keys. The order may be specified by prepending each of the keys by a + or a -. Ascending order is assumed.

Parameters:keys – fields to order the query results by; keys may be prefixed with + or - to determine the ordering direction
read_preference(read_preference)

Change the read_preference when querying.

Parameters:read_preference – override ReplicaSetConnection-level preference.
rewind()

Rewind the cursor to its unevaluated state.

New in version 0.3.

scalar(*fields)

Instead of returning Document instances, return either a specific value or a tuple of values in order.

Can be used along with no_dereference() to turn off dereferencing.

Note

This effects all results and can be unset by calling scalar without arguments. Calls only automatically.

Parameters:fields – One or more fields to return instead of a Document.

Handles dereferencing of DBRef objects or ObjectId a maximum depth in order to cut down the number queries to mongodb.

New in version 0.5.

skip(n)

Skip n documents before returning the results. This may also be achieved using array-slicing syntax (e.g. User.objects[5:]).

Parameters:n – the number of objects to skip before returning results
slave_okay(enabled)

Enable or disable the slave_okay when querying.

Parameters:enabled – whether or not the slave_okay is enabled
snapshot(enabled)

Enable or disable snapshot mode when querying.

Parameters:enabled – whether or not snapshot mode is enabled

..versionchanged:: 0.5 - made chainable

sum(field)

Sum over the values of the specified field.

Parameters:field – the field to sum over; use dot-notation to refer to embedded document fields

Changed in version 0.5: - updated to map_reduce as db.eval doesnt work with sharding.

timeout(enabled)

Enable or disable the default mongod timeout when querying.

Parameters:enabled – whether or not the timeout is used

..versionchanged:: 0.5 - made chainable

to_json(*args, **kwargs)

Converts a queryset to JSON

update(upsert=False, multi=True, write_concern=None, full_result=False, **update)

Perform an atomic update on the fields matched by the query.

Parameters:
  • upsert – Any existing document with that “_id” is overwritten.
  • multi – Update multiple documents.
  • write_concern – Extra keyword arguments are passed down which will be used as options for the resultant getLastError command. For example, save(..., write_concern={w: 2, fsync: True}, ...) will wait until at least two servers have recorded the write and will force an fsync on the primary server.
  • full_result – Return the full result rather than just the number updated.
  • update – Django-style update keyword arguments

New in version 0.2.

update_one(upsert=False, write_concern=None, **update)

Perform an atomic update on first field matched by the query.

Parameters:
  • upsert – Any existing document with that “_id” is overwritten.
  • write_concern – Extra keyword arguments are passed down which will be used as options for the resultant getLastError command. For example, save(..., write_concern={w: 2, fsync: True}, ...) will wait until at least two servers have recorded the write and will force an fsync on the primary server.
  • update – Django-style update keyword arguments

New in version 0.2.

values_list(*fields)

An alias for scalar

where(where_clause)

Filter QuerySet results with a $where clause (a Javascript expression). Performs automatic field name substitution like mongoengine.queryset.Queryset.exec_js().

Note

When using this mode of query, the database will call your function, or evaluate your predicate clause, for each object in the collection.

New in version 0.5.

with_id(object_id)

Retrieve the object matching the id provided. Uses object_id only and raises InvalidQueryError if a filter has been applied. Returns None if no document exists with that id.

Parameters:object_id – the value for the id of the document to look up

Changed in version 0.6: Raises InvalidQueryError if filter has been set

class mongoengine.queryset.QuerySetNoCache(document, collection)

A non caching QuerySet

__call__(q_obj=None, class_check=True, slave_okay=False, read_preference=None, **query)

Filter the selected documents by calling the QuerySet with a query.

Parameters:
  • q_obj – a Q object to be used in the query; the QuerySet is filtered multiple times with different Q objects, only the last one will be used
  • class_check – If set to False bypass class name check when querying collection
  • slave_okay – if True, allows this query to be run against a replica secondary.
  • query – Django-style query keyword arguments
Params read_preference:
 

if set, overrides connection-level read_preference from ReplicaSetConnection.
cache()

Convert to a caching queryset

New in version 0.8.3: Convert to caching queryset

mongoengine.queryset.queryset_manager(func)

Decorator that allows you to define custom QuerySet managers on Document classes. The manager must be a function that accepts a Document class as its first argument, and a QuerySet as its second argument. The method function should return a QuerySet, probably the same one that was passed in, but modified in some way.

3.5. Fields

class mongoengine.base.fields.BaseField(db_field=None, name=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, verbose_name=None, help_text=None)

A base class for fields in a MongoDB document. Instances of this class may be added to subclasses of Document to define a document’s schema.

Changed in version 0.5: - added verbose and help text

Parameters:
  • db_field – The database field to store this field in (defaults to the name of the field)
  • name – Depreciated - use db_field
  • required – If the field is required. Whether it has to have a value or not. Defaults to False.
  • default – (optional) The default value for this field if no value has been set (or if the value has been unset). It Can be a callable.
  • unique – Is the field value unique or not. Defaults to False.
  • unique_with – (optional) The other field this field should be unique with.
  • primary_key – Mark this field as the primary key. Defaults to False.
  • validation – (optional) A callable to validate the value of the field. Generally this is deprecated in favour of the FIELD.validate method
  • choices – (optional) The valid choices
  • verbose_name – (optional) The verbose name for the field. Designed to be human readable and is often used when generating model forms from the document model.
  • help_text – (optional) The help text for this field and is often used when generating model forms from the document model.
class mongoengine.fields.StringField(regex=None, max_length=None, min_length=None, **kwargs)

A unicode string field.

class mongoengine.fields.URLField(verify_exists=False, url_regex=None, **kwargs)

A field that validates input as an URL.

New in version 0.3.

class mongoengine.fields.EmailField(regex=None, max_length=None, min_length=None, **kwargs)

A field that validates input as an E-Mail-Address.

New in version 0.4.

class mongoengine.fields.IntField(min_value=None, max_value=None, **kwargs)

An 32-bit integer field.

class mongoengine.fields.LongField(min_value=None, max_value=None, **kwargs)

An 64-bit integer field.

class mongoengine.fields.FloatField(min_value=None, max_value=None, **kwargs)

An floating point number field.

class mongoengine.fields.DecimalField(min_value=None, max_value=None, force_string=False, precision=2, rounding='ROUND_HALF_UP', **kwargs)

A fixed-point decimal number field.

Changed in version 0.8.

New in version 0.3.

Parameters:
  • min_value – Validation rule for the minimum acceptable value.
  • max_value – Validation rule for the maximum acceptable value.
  • force_string – Store as a string.
  • precision – Number of decimal places to store.
  • rounding –

    The rounding rule from the python decimal libary:

    • decimal.ROUND_CEILING (towards Infinity)
    • decimal.ROUND_DOWN (towards zero)
    • decimal.ROUND_FLOOR (towards -Infinity)
    • decimal.ROUND_HALF_DOWN (to nearest with ties going towards zero)
    • decimal.ROUND_HALF_EVEN (to nearest with ties going to nearest even integer)
    • decimal.ROUND_HALF_UP (to nearest with ties going away from zero)
    • decimal.ROUND_UP (away from zero)
    • decimal.ROUND_05UP (away from zero if last digit after rounding towards zero would have been 0 or 5; otherwise towards zero)

    Defaults to: decimal.ROUND_HALF_UP
class mongoengine.fields.BooleanField(db_field=None, name=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, verbose_name=None, help_text=None)

A boolean field type.

New in version 0.1.2.

Parameters:
  • db_field – The database field to store this field in (defaults to the name of the field)
  • name – Depreciated - use db_field
  • required – If the field is required. Whether it has to have a value or not. Defaults to False.
  • default – (optional) The default value for this field if no value has been set (or if the value has been unset). It Can be a callable.
  • unique – Is the field value unique or not. Defaults to False.
  • unique_with – (optional) The other field this field should be unique with.
  • primary_key – Mark this field as the primary key. Defaults to False.
  • validation – (optional) A callable to validate the value of the field. Generally this is deprecated in favour of the FIELD.validate method
  • choices – (optional) The valid choices
  • verbose_name – (optional) The verbose name for the field. Designed to be human readable and is often used when generating model forms from the document model.
  • help_text – (optional) The help text for this field and is often used when generating model forms from the document model.
class mongoengine.fields.DateTimeField(db_field=None, name=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, verbose_name=None, help_text=None)

A datetime field.

Uses the python-dateutil library if available alternatively use time.strptime to parse the dates. Note: python-dateutil’s parser is fully featured and when installed you can utilise it to convert varing types of date formats into valid python datetime objects.

Note: Microseconds are rounded to the nearest millisecond.
Pre UTC microsecond support is effecively broken. Use ComplexDateTimeField if you need accurate microsecond support.
Parameters:
  • db_field – The database field to store this field in (defaults to the name of the field)
  • name – Depreciated - use db_field
  • required – If the field is required. Whether it has to have a value or not. Defaults to False.
  • default – (optional) The default value for this field if no value has been set (or if the value has been unset). It Can be a callable.
  • unique – Is the field value unique or not. Defaults to False.
  • unique_with – (optional) The other field this field should be unique with.
  • primary_key – Mark this field as the primary key. Defaults to False.
  • validation – (optional) A callable to validate the value of the field. Generally this is deprecated in favour of the FIELD.validate method
  • choices – (optional) The valid choices
  • verbose_name – (optional) The verbose name for the field. Designed to be human readable and is often used when generating model forms from the document model.
  • help_text – (optional) The help text for this field and is often used when generating model forms from the document model.
class mongoengine.fields.ComplexDateTimeField(separator=', ', **kwargs)

ComplexDateTimeField handles microseconds exactly instead of rounding like DateTimeField does.

Derives from a StringField so you can do gte and lte filtering by using lexicographical comparison when filtering / sorting strings.

The stored string has the following format:

YYYY,MM,DD,HH,MM,SS,NNNNNN

Where NNNNNN is the number of microseconds of the represented datetime. The , as the separator can be easily modified by passing the separator keyword when initializing the field.

New in version 0.5.

class mongoengine.fields.EmbeddedDocumentField(document_type, **kwargs)

An embedded document field - with a declared document_type. Only valid values are subclasses of EmbeddedDocument.

class mongoengine.fields.GenericEmbeddedDocumentField(db_field=None, name=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, verbose_name=None, help_text=None)

A generic embedded document field - allows any EmbeddedDocument to be stored.

Only valid values are subclasses of EmbeddedDocument.

Note

You can use the choices param to limit the acceptable EmbeddedDocument types

Parameters:
  • db_field – The database field to store this field in (defaults to the name of the field)
  • name – Depreciated - use db_field
  • required – If the field is required. Whether it has to have a value or not. Defaults to False.
  • default – (optional) The default value for this field if no value has been set (or if the value has been unset). It Can be a callable.
  • unique – Is the field value unique or not. Defaults to False.
  • unique_with – (optional) The other field this field should be unique with.
  • primary_key – Mark this field as the primary key. Defaults to False.
  • validation – (optional) A callable to validate the value of the field. Generally this is deprecated in favour of the FIELD.validate method
  • choices – (optional) The valid choices
  • verbose_name – (optional) The verbose name for the field. Designed to be human readable and is often used when generating model forms from the document model.
  • help_text – (optional) The help text for this field and is often used when generating model forms from the document model.
class mongoengine.fields.DynamicField(db_field=None, name=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, verbose_name=None, help_text=None)

A truly dynamic field type capable of handling different and varying types of data.

Used by DynamicDocument to handle dynamic data

Parameters:
  • db_field – The database field to store this field in (defaults to the name of the field)
  • name – Depreciated - use db_field
  • required – If the field is required. Whether it has to have a value or not. Defaults to False.
  • default – (optional) The default value for this field if no value has been set (or if the value has been unset). It Can be a callable.
  • unique – Is the field value unique or not. Defaults to False.
  • unique_with – (optional) The other field this field should be unique with.
  • primary_key – Mark this field as the primary key. Defaults to False.
  • validation – (optional) A callable to validate the value of the field. Generally this is deprecated in favour of the FIELD.validate method
  • choices – (optional) The valid choices
  • verbose_name – (optional) The verbose name for the field. Designed to be human readable and is often used when generating model forms from the document model.
  • help_text – (optional) The help text for this field and is often used when generating model forms from the document model.
class mongoengine.fields.ListField(field=None, **kwargs)

A list field that wraps a standard field, allowing multiple instances of the field to be used as a list in the database.

If using with ReferenceFields see: One to Many with ListFields

Note

Required means it cannot be empty - as the default for ListFields is []

class mongoengine.fields.SortedListField(field, **kwargs)

A ListField that sorts the contents of its list before writing to the database in order to ensure that a sorted list is always retrieved.

Warning

There is a potential race condition when handling lists. If you set / save the whole list then other processes trying to save the whole list as well could overwrite changes. The safest way to append to a list is to perform a push operation.

New in version 0.4.

Changed in version 0.6: - added reverse keyword

class mongoengine.fields.DictField(basecls=None, field=None, *args, **kwargs)

A dictionary field that wraps a standard Python dictionary. This is similar to an embedded document, but the structure is not defined.

Note

Required means it cannot be empty - as the default for ListFields is []

New in version 0.3.

Changed in version 0.5: - Can now handle complex / varying types of data

class mongoengine.fields.MapField(field=None, *args, **kwargs)

A field that maps a name to a specified field type. Similar to a DictField, except the ‘value’ of each item must match the specified field type.

New in version 0.5.

class mongoengine.fields.ReferenceField(document_type, dbref=False, reverse_delete_rule=0, **kwargs)

A reference to a document that will be automatically dereferenced on access (lazily).

Use the reverse_delete_rule to handle what should happen if the document the field is referencing is deleted. EmbeddedDocuments, DictFields and MapFields do not support reverse_delete_rules and an InvalidDocumentError will be raised if trying to set on one of these Document / Field types.

The options are:

  • DO_NOTHING - don’t do anything (default).

  • NULLIFY - Updates the reference to null.

  • CASCADE - Deletes the documents associated with the reference.

  • DENY - Prevent the deletion of the reference object.

  • PULL - Pull the reference from a ListField

    of references

Alternative syntax for registering delete rules (useful when implementing bi-directional delete rules)

class Bar(Document):
    content = StringField()
    foo = ReferenceField('Foo')

Bar.register_delete_rule(Foo, 'bar', NULLIFY)

Note

reverse_delete_rules do not trigger pre / post delete signals to be triggered.

Changed in version 0.5: added reverse_delete_rule

Initialises the Reference Field.

Parameters:
  • dbref – Store the reference as DBRef or as the ObjectId.id .
  • reverse_delete_rule – Determines what to do when the referring object is deleted
class mongoengine.fields.GenericReferenceField(db_field=None, name=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, verbose_name=None, help_text=None)

A reference to any Document subclass that will be automatically dereferenced on access (lazily).

Note

  • Any documents used as a generic reference must be registered in the document registry. Importing the model will automatically register it.
  • You can use the choices param to limit the acceptable Document types

New in version 0.3.

Parameters:
  • db_field – The database field to store this field in (defaults to the name of the field)
  • name – Depreciated - use db_field
  • required – If the field is required. Whether it has to have a value or not. Defaults to False.
  • default – (optional) The default value for this field if no value has been set (or if the value has been unset). It Can be a callable.
  • unique – Is the field value unique or not. Defaults to False.
  • unique_with – (optional) The other field this field should be unique with.
  • primary_key – Mark this field as the primary key. Defaults to False.
  • validation – (optional) A callable to validate the value of the field. Generally this is deprecated in favour of the FIELD.validate method
  • choices – (optional) The valid choices
  • verbose_name – (optional) The verbose name for the field. Designed to be human readable and is often used when generating model forms from the document model.
  • help_text – (optional) The help text for this field and is often used when generating model forms from the document model.
class mongoengine.fields.BinaryField(max_bytes=None, **kwargs)

A binary data field.

class mongoengine.fields.FileField(db_alias='default', collection_name='fs', **kwargs)

A GridFS storage field.

New in version 0.4.

Changed in version 0.5: added optional size param for read

Changed in version 0.6: added db_alias for multidb support

class mongoengine.fields.ImageField(size=None, thumbnail_size=None, collection_name='images', **kwargs)

A Image File storage field.

@size (width, height, force):
max size to store images, if larger will be automatically resized ex: size=(800, 600, True)
@thumbnail (width, height, force):
size to generate a thumbnail

New in version 0.6.

class mongoengine.fields.SequenceField(collection_name=None, db_alias=None, sequence_name=None, value_decorator=None, *args, **kwargs)
Provides a sequental counter see:
http://www.mongodb.org/display/DOCS/Object+IDs#ObjectIDs-SequenceNumbers

Note

Although traditional databases often use increasing sequence numbers for primary keys. In MongoDB, the preferred approach is to use Object IDs instead. The concept is that in a very large cluster of machines, it is easier to create an object ID than have global, uniformly increasing sequence numbers.

Use any callable as value_decorator to transform calculated counter into any value suitable for your needs, e.g. string or hexadecimal representation of the default integer counter value.

New in version 0.5.

Changed in version 0.8: added value_decorator

class mongoengine.fields.ObjectIdField(db_field=None, name=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, verbose_name=None, help_text=None)

A field wrapper around MongoDB’s ObjectIds.

Parameters:
  • db_field – The database field to store this field in (defaults to the name of the field)
  • name – Depreciated - use db_field
  • required – If the field is required. Whether it has to have a value or not. Defaults to False.
  • default – (optional) The default value for this field if no value has been set (or if the value has been unset). It Can be a callable.
  • unique – Is the field value unique or not. Defaults to False.
  • unique_with – (optional) The other field this field should be unique with.
  • primary_key – Mark this field as the primary key. Defaults to False.
  • validation – (optional) A callable to validate the value of the field. Generally this is deprecated in favour of the FIELD.validate method
  • choices – (optional) The valid choices
  • verbose_name – (optional) The verbose name for the field. Designed to be human readable and is often used when generating model forms from the document model.
  • help_text – (optional) The help text for this field and is often used when generating model forms from the document model.
class mongoengine.fields.UUIDField(binary=True, **kwargs)

A UUID field.

New in version 0.6.

Store UUID data in the database

Parameters:binary – if False store as a string.

Changed in version 0.8.0.

Changed in version 0.6.19.

class mongoengine.fields.GeoPointField(db_field=None, name=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, verbose_name=None, help_text=None)

A list storing a latitude and longitude.

New in version 0.4.

Parameters:
  • db_field – The database field to store this field in (defaults to the name of the field)
  • name – Depreciated - use db_field
  • required – If the field is required. Whether it has to have a value or not. Defaults to False.
  • default – (optional) The default value for this field if no value has been set (or if the value has been unset). It Can be a callable.
  • unique – Is the field value unique or not. Defaults to False.
  • unique_with – (optional) The other field this field should be unique with.
  • primary_key – Mark this field as the primary key. Defaults to False.
  • validation – (optional) A callable to validate the value of the field. Generally this is deprecated in favour of the FIELD.validate method
  • choices – (optional) The valid choices
  • verbose_name – (optional) The verbose name for the field. Designed to be human readable and is often used when generating model forms from the document model.
  • help_text – (optional) The help text for this field and is often used when generating model forms from the document model.
class mongoengine.fields.PointField(auto_index=True, *args, **kwargs)

A geo json field storing a latitude and longitude.

The data is represented as:

{ "type" : "Point" ,
  "coordinates" : [x, y]}

You can either pass a dict with the full information or a list to set the value.

Requires mongodb >= 2.4 .. versionadded:: 0.8

Parameters:auto_index – Automatically create a “2dsphere” index. Defaults to True.
class mongoengine.fields.LineStringField(auto_index=True, *args, **kwargs)

A geo json field storing a line of latitude and longitude coordinates.

The data is represented as:

{ "type" : "LineString" ,
  "coordinates" : [[x1, y1], [x1, y1] ... [xn, yn]]}

You can either pass a dict with the full information or a list of points.

Requires mongodb >= 2.4 .. versionadded:: 0.8

Parameters:auto_index – Automatically create a “2dsphere” index. Defaults to True.
class mongoengine.fields.PolygonField(auto_index=True, *args, **kwargs)

A geo json field storing a polygon of latitude and longitude coordinates.

The data is represented as:

{ "type" : "Polygon" ,
  "coordinates" : [[[x1, y1], [x1, y1] ... [xn, yn]],
                   [[x1, y1], [x1, y1] ... [xn, yn]]}

You can either pass a dict with the full information or a list of LineStrings. The first LineString being the outside and the rest being holes.

Requires mongodb >= 2.4 .. versionadded:: 0.8

Parameters:auto_index – Automatically create a “2dsphere” index. Defaults to True.
class mongoengine.fields.GridFSError
class mongoengine.fields.GridFSProxy(grid_id=None, key=None, instance=None, db_alias='default', collection_name='fs')

Proxy object to handle writing and reading of files to and from GridFS

New in version 0.4.

Changed in version 0.5: - added optional size param to read

Changed in version 0.6: - added collection name param

class mongoengine.fields.ImageGridFsProxy(grid_id=None, key=None, instance=None, db_alias='default', collection_name='fs')

Proxy for ImageField

versionadded: 0.6

class mongoengine.fields.ImproperlyConfigured

3.6. Misc

mongoengine.common._import_class(cls_name)

Cache mechanism for imports.

Due to complications of circular imports mongoengine needs to do lots of inline imports in functions. This is inefficient as classes are imported repeated throughout the mongoengine code. This is compounded by some recursive functions requiring inline imports.

mongoengine.common provides a single point to import all these classes. Circular imports aren’t an issue as it dynamically imports the class when first needed. Subsequent calls to the _import_class() can then directly retrieve the class from the mongoengine.common._class_registry_cache.