3. API Reference¶

3.1. Connecting¶

mongoengine.connect(db=None, 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: program: mongod.

In order to replace a connection identified by a given alias, you’ll need to call disconnect first

See the docstring for register_connection for more details about all supported kwargs.

mongoengine.register_connection(alias, db=None, name=None, host=None, port=None, read_preference=Primary(), username=None, password=None, authentication_source=None, authentication_mechanism=None, **kwargs)¶

Register the connection settings.

: param alias: the name that will be used to refer to this connection: throughout MongoEngine

: param db: the name of the database to use, for compatibility with connect : param name: the name of the specific database to use : param host: the host name of the: program: mongod instance to connect to : param port: the port that the: program: mongod instance is running on : param read_preference: The read preference for the collection : param username: username to authenticate with : param password: password to authenticate with : param authentication_source: database to authenticate against : param authentication_mechanism: database authentication mechanisms.

By default, use SCRAM-SHA-1 with MongoDB 3.0 and later, MONGODB-CR (MongoDB Challenge Response protocol) for older servers.

: param is_mock: explicitly use mongomock for this connection: (can also be done by using `mongomock: // ` as db host prefix)
: param kwargs: ad-hoc parameters to be passed into the pymongo driver,: for example maxpoolsize, tz_aware, etc. See the documentation for pymongo’s MongoClient for a full list.

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 snake_case. 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 enable this behaviourset allow_inheritance to True 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. max_size is rounded up to the next multiple of 256 by MongoDB internally and mongoengine before. Use also a multiple of 256 to avoid confusions. If max_size is not specified and max_documents is, max_size defaults to 10485760 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 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.

By default, any extra attribute existing in stored data but not declared in your model will raise a FieldDoesNotExist error. This can be disabled by setting strict to False in the meta dictionary.

Initialise a document or an embedded document.

Parameters

values – A dictionary of keys and values for the document. It may contain additional reserved keywords, e.g. “__auto_convert”.
__auto_convert – If True, supplied values will be converted to Python-type values via each field’s to_python method.
_created – Indicates whether this is a brand new document or whether it’s already been persisted before. Defaults to true.

objects¶: A QuerySet object that is created lazily on access.

cascade_save(**kwargs)¶: Recursively save any references and generic references on the document.

clean()¶

Hook for doing document level data cleaning (usually validation or assignment) before validation is run.

Any ValidationError raised by this method will not be associated with a particular field; it will have a special-case association with the field defined by NON_FIELD_ERRORS.

classmethod compare_indexes()¶: Compares the indexes defined in MongoEngine with the ones existing in the database. Returns any missing/extra indexes.

classmethod create_index(keys, background=False, **kwargs)¶

Creates the given indexes if required.

Parameters

keys – 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
background – Allows index creation in the background

delete(signal_kwargs=None, **write_concern)¶

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

Parameters

signal_kwargs – (optional) kwargs dictionary to be passed to the signal calls.
write_concern – Extra keyword arguments are passed down which will be used as options for the resultant getLastError command. For example, save(..., 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.

Raises OperationError if the document has no collection set (i.g. if it is abstract)

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

Ensure that the given indexes are in place. Deprecated in favour of create_index.

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
background – Allows index creation in the background

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 from_json(json_data, created=False)¶

Converts json data to a Document instance

Parameters

json_data (str) – The json data to load into the Document
created (bool) –
Boolean defining whether to consider the newly instantiated document as brand new or as persisted already: * If True, consider the document as brand new, no matter what data

it’s loaded with (i.e. even if an ID is loaded).
- If False and an ID is NOT provided, consider the document as brand new.
- If False and an ID is provided, assume that the object has already been persisted (this has an impact on the subsequent call to .save()).
- Defaults to False.

get_text_score()¶: Get text score from text query

classmethod list_indexes()¶: Lists all of the indexes that should be created for given collection. It includes all the indexes from super- and sub-classes.

modify(query=None, **update)¶

Perform an atomic update of the document in the database and reload the document object using updated version.

Returns True if the document has been updated or False if the document in the database doesn’t match the query.

Note

All unsaved changes that have been made to the document are rejected if the method returns True.

Parameters

query – the update will be performed only if the document in the database matches the query
update – Django-style update keyword arguments

my_metaclass¶: alias of mongoengine.base.metaclasses.TopLevelDocumentMetaclass

property pk¶: Get the primary key.

classmethod register_delete_rule(document_cls, field_name, rule)¶: This method registers the delete rules to apply when removing this object.

reload(*fields, **kwargs)¶

Reloads all attributes from the database.

Parameters

fields – (optional) args list of fields to reload
max_depth – (optional) depth of dereferencing to follow

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

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

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
save_condition – only perform save if matching record in db satisfies condition(s) (e.g. version number). Raises OperationError if the conditions are not satisfied
signal_kwargs – (optional) kwargs dictionary to be passed to the signal calls.

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.

select_related(max_depth=1)¶: Handles dereferencing of DBRef objects to a maximum depth in order to cut down the number queries to mongodb.

switch_collection(collection_name, keep_created=True)¶

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()

Parameters

collection_name (str) – The database alias to use for saving the document
keep_created (bool) – keep self._created value after switching collection, else is reset to True

See also

Use switch_db if you need to read from another database

switch_db(db_alias, keep_created=True)¶

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()

Parameters

db_alias (str) – The database alias to use for saving the document
keep_created (bool) – keep self._created value after switching db, else is reset to True

See also

Use switch_collection if you need to read from another collection

to_dbref()¶: Returns an instance of DBRef useful in __raw__ queries.

to_json(*args, **kwargs)¶

Convert this document to JSON.

Parameters: use_db_field – Serialize field names as they appear in MongoDB (as opposed to attribute names on this document). Defaults to True.

to_mongo(*args, **kwargs)¶: Return as SON data ready for use with MongoDB.

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.

validate(clean=True)¶

Ensure that all fields’ values are valid and that required fields are present.

Raises ValidationError if any of the fields’ values are found to be invalid.

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 enable this behaviour set allow_inheritance to True in the meta dictionary.

Initialise a document or an embedded document.

Parameters

values – A dictionary of keys and values for the document. It may contain additional reserved keywords, e.g. “__auto_convert”.
__auto_convert – If True, supplied values will be converted to Python-type values via each field’s to_python method.
_created – Indicates whether this is a brand new document or whether it’s already been persisted before. Defaults to true.

clean()¶

Hook for doing document level data cleaning (usually validation or assignment) before validation is run.

Any ValidationError raised by this method will not be associated with a particular field; it will have a special-case association with the field defined by NON_FIELD_ERRORS.

classmethod from_json(json_data, created=False)¶

Converts json data to a Document instance

Parameters

json_data (str) – The json data to load into the Document
created (bool) –
Boolean defining whether to consider the newly instantiated document as brand new or as persisted already: * If True, consider the document as brand new, no matter what data

it’s loaded with (i.e. even if an ID is loaded).
- If False and an ID is NOT provided, consider the document as brand new.
- If False and an ID is provided, assume that the object has already been persisted (this has an impact on the subsequent call to .save()).
- Defaults to False.

get_text_score()¶: Get text score from text query

my_metaclass¶: alias of mongoengine.base.metaclasses.DocumentMetaclass

to_json(*args, **kwargs)¶

Convert this document to JSON.

Parameters: use_db_field – Serialize field names as they appear in MongoDB (as opposed to attribute names on this document). Defaults to True.

to_mongo(*args, **kwargs)¶: Return as SON data ready for use with MongoDB.

validate(clean=True)¶

Ensure that all fields’ values are valid and that required fields are present.

Raises ValidationError if any of the fields’ values are found to be invalid.

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 expanded 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: undeclared fields cannot start with _

Initialise a document or an embedded document.

Parameters

values – A dictionary of keys and values for the document. It may contain additional reserved keywords, e.g. “__auto_convert”.
__auto_convert – If True, supplied values will be converted to Python-type values via each field’s to_python method.
_created – Indicates whether this is a brand new document or whether it’s already been persisted before. Defaults to true.

cascade_save(**kwargs)¶: Recursively save any references and generic references on the document.

clean()¶

Hook for doing document level data cleaning (usually validation or assignment) before validation is run.

Any ValidationError raised by this method will not be associated with a particular field; it will have a special-case association with the field defined by NON_FIELD_ERRORS.

classmethod compare_indexes()¶: Compares the indexes defined in MongoEngine with the ones existing in the database. Returns any missing/extra indexes.

classmethod create_index(keys, background=False, **kwargs)¶

Creates the given indexes if required.

Parameters

keys – 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
background – Allows index creation in the background

delete(signal_kwargs=None, **write_concern)¶

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

Parameters

signal_kwargs – (optional) kwargs dictionary to be passed to the signal calls.
write_concern – Extra keyword arguments are passed down which will be used as options for the resultant getLastError command. For example, save(..., 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.

Raises OperationError if the document has no collection set (i.g. if it is abstract)

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

Ensure that the given indexes are in place. Deprecated in favour of create_index.

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
background – Allows index creation in the background

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 from_json(json_data, created=False)¶

Converts json data to a Document instance

Parameters

json_data (str) – The json data to load into the Document
created (bool) –
Boolean defining whether to consider the newly instantiated document as brand new or as persisted already: * If True, consider the document as brand new, no matter what data

it’s loaded with (i.e. even if an ID is loaded).
- If False and an ID is NOT provided, consider the document as brand new.
- If False and an ID is provided, assume that the object has already been persisted (this has an impact on the subsequent call to .save()).
- Defaults to False.

get_text_score()¶: Get text score from text query

classmethod list_indexes()¶: Lists all of the indexes that should be created for given collection. It includes all the indexes from super- and sub-classes.

modify(query=None, **update)¶

Perform an atomic update of the document in the database and reload the document object using updated version.

Returns True if the document has been updated or False if the document in the database doesn’t match the query.

Note

All unsaved changes that have been made to the document are rejected if the method returns True.

Parameters

query – the update will be performed only if the document in the database matches the query
update – Django-style update keyword arguments

my_metaclass¶: alias of mongoengine.base.metaclasses.TopLevelDocumentMetaclass

property pk¶: Get the primary key.

classmethod register_delete_rule(document_cls, field_name, rule)¶: This method registers the delete rules to apply when removing this object.

reload(*fields, **kwargs)¶

Reloads all attributes from the database.

Parameters

fields – (optional) args list of fields to reload
max_depth – (optional) depth of dereferencing to follow

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

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

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
save_condition – only perform save if matching record in db satisfies condition(s) (e.g. version number). Raises OperationError if the conditions are not satisfied
signal_kwargs – (optional) kwargs dictionary to be passed to the signal calls.

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.

select_related(max_depth=1)¶: Handles dereferencing of DBRef objects to a maximum depth in order to cut down the number queries to mongodb.

switch_collection(collection_name, keep_created=True)¶

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()

Parameters

collection_name (str) – The database alias to use for saving the document
keep_created (bool) – keep self._created value after switching collection, else is reset to True

See also

Use switch_db if you need to read from another database

switch_db(db_alias, keep_created=True)¶

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()

Parameters

db_alias (str) – The database alias to use for saving the document
keep_created (bool) – keep self._created value after switching db, else is reset to True

See also

Use switch_collection if you need to read from another collection

to_dbref()¶: Returns an instance of DBRef useful in __raw__ queries.

to_json(*args, **kwargs)¶

Convert this document to JSON.

Parameters: use_db_field – Serialize field names as they appear in MongoDB (as opposed to attribute names on this document). Defaults to True.

to_mongo(*args, **kwargs)¶: Return as SON data ready for use with MongoDB.

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.

validate(clean=True)¶

Ensure that all fields’ values are valid and that required fields are present.

Raises ValidationError if any of the fields’ values are found to be invalid.

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

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

Initialise a document or an embedded document.

Parameters

values – A dictionary of keys and values for the document. It may contain additional reserved keywords, e.g. “__auto_convert”.
__auto_convert – If True, supplied values will be converted to Python-type values via each field’s to_python method.
_created – Indicates whether this is a brand new document or whether it’s already been persisted before. Defaults to true.

clean()¶

Hook for doing document level data cleaning (usually validation or assignment) before validation is run.

Any ValidationError raised by this method will not be associated with a particular field; it will have a special-case association with the field defined by NON_FIELD_ERRORS.

classmethod from_json(json_data, created=False)¶

Converts json data to a Document instance

Parameters

json_data (str) – The json data to load into the Document
created (bool) –
Boolean defining whether to consider the newly instantiated document as brand new or as persisted already: * If True, consider the document as brand new, no matter what data

it’s loaded with (i.e. even if an ID is loaded).
- If False and an ID is NOT provided, consider the document as brand new.
- If False and an ID is provided, assume that the object has already been persisted (this has an impact on the subsequent call to .save()).
- Defaults to False.

get_text_score()¶: Get text score from text query

my_metaclass¶: alias of mongoengine.base.metaclasses.DocumentMetaclass

to_json(*args, **kwargs)¶

Convert this document to JSON.

Parameters: use_db_field – Serialize field names as they appear in MongoDB (as opposed to attribute names on this document). Defaults to True.

to_mongo(*args, **kwargs)¶: Return as SON data ready for use with MongoDB.

validate(clean=True)¶

Ensure that all fields’ values are valid and that required fields are present.

Raises ValidationError if any of the fields’ values are found to be invalid.

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.

property 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.

class mongoengine.FieldDoesNotExist¶

Raised when trying to set a field not declared in a Document or an EmbeddedDocument.

To avoid this behavior on data loading, you should set the strict to False in the meta dictionary.

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.switch_collection(cls, collection_name)¶

switch_collection alias context manager.

Example

class Group(Document):
    name = StringField()

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

with switch_collection(Group, 'group1') as Group:
    Group(name='hello testdb!').save()  # Saves in group1 collection

Construct the switch_collection context manager.

Parameters

cls – the class to change the registered db
collection_name – the name of the collection 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(alias='default')¶

Query_counter context manager to get the number of queries. This works by updating the profiling_level of the database so that all queries get logged, resetting the db.system.profile collection at the beginning of the context and counting the new entries.

This was designed for debugging purpose. In fact it is a global counter so queries issued by other threads/processes can interfere with it

Be aware that: - Iterating over large amount of documents (>101) makes pymongo issue getmore queries to fetch the next batch of

documents (https://docs.mongodb.com/manual/tutorial/iterate-a-cursor/#cursor-batches)

Some queries are ignored by default by the counter (killcursors, db.system.indexes)

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, **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.
query – Django-style query keyword arguments.

aggregate(pipeline, *suppl_pipeline, **kwargs)¶

Perform a aggregate function based in your queryset params

Parameters

pipeline – list of aggregation commands, see: http://docs.mongodb.org/manual/core/aggregation-pipeline/
suppl_pipeline – unpacked list of pipeline (added to support deprecation of the old interface) parameter will be removed shortly
kwargs – (optional) kwargs dictionary to be passed to pymongo’s aggregate call See https://api.mongodb.com/python/current/api/pymongo/collection.html#pymongo.collection.Collection.aggregate

all()¶: Returns a copy of the current QuerySet.

all_fields()¶

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

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

allow_disk_use(enabled)¶

Enable or disable the use of temporary files on disk while processing a blocking sort operation.: (To store data exceeding the 100 megabyte system memory limit)

Parameters: enabled – whether or not temporary files on disk are used

as_pymongo()¶

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

This method is particularly useful if you don’t need dereferencing and care primarily about the speed of data retrieval.

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

batch_size(size)¶

Limit the number of documents returned in a single batch (each batch requires a round trip to the server).

See http://api.mongodb.com/python/current/api/pymongo/cursor.html#pymongo.cursor.Cursor.batch_size for details.

Parameters: size – desired size of each batch.

clear_cls_query()¶

Clear the default “_cls” query.

By default, all queries generated for documents that allow inheritance include an extra “_cls” clause. In most cases this is desirable, but sometimes you might achieve better performance if you clear that default query.

Scan the code for _cls_query to get more details.

clone()¶: Create a copy of the current queryset.

collation(collation=None)¶

Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks. :param collation: ~pymongo.collation.Collation or dict with following fields:

{
locale: str, caseLevel: bool, caseFirst: str, strength: int, numericOrdering: bool, alternate: str, maxVariable: str, backwards: str

}

Collation should be added to indexes like in test example

comment(text)¶

Add a comment to the query.

See https://docs.mongodb.com/manual/reference/method/cursor.comment/#cursor.comment for details.

count(with_limit_and_skip=False)¶

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.

delete(write_concern=None, _from_doc_delete=False, cascade_refs=None)¶

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.

:returns number of deleted documents

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.

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

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()¶: Return an explain plan record for the QuerySet cursor.

fields(_only_called=False, **kwargs)¶

Manipulate how you load this document’s fields. Used by .only() and .exclude() to manipulate which fields to retrieve. If called directly, use a set of kwargs similar to the MongoDB projection document. For example:

Include only a subset of fields:

posts = BlogPost.objects(…).fields(author=1, title=1)

Exclude a specific field:

posts = BlogPost.objects(…).fields(comments=0)

To retrieve a subrange or sublist of array elements, support exist for both the slice and elemMatch projection operator:

posts = BlogPost.objects(…).fields(slice__comments=5) posts = BlogPost.objects(…).fields(elemMatch__comments=”test”)

Parameters: kwargs – A set of keyword arguments identifying what to include, exclude, or slice.

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.

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.

in_bulk(object_ids)¶

“Retrieve a set of documents by their ids.

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

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

bulk insert documents

Parameters

doc_or_docs – 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.
signal_kwargs – (optional) kwargs dictionary to be passed to the signal calls.

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

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 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

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 if n is greater than 0.

When 0 is passed, returns all the documents in the cursor

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.

max_time_ms(ms)¶

Wait ms milliseconds before killing the query on the server

Parameters: ms – the number of milliseconds before killing the query on the server

modify(upsert=False, full_response=False, remove=False, new=False, **update)¶

Update and return the updated document.

Returns either the document before or after modification based on new parameter. If no documents match the query and upsert is false, returns None. If upserting and new is false, returns None.

If the full_response parameter is True, the return value will be the entire response object from the server, including the ‘ok’ and ‘lastErrorObject’ fields, rather than just the modified document. This is useful mainly because the ‘lastErrorObject’ document holds information about the command’s execution.

Parameters

upsert – insert if document doesn’t exist (default False)
full_response – return the entire response object from the server (default False, not available for PyMongo 3+)
remove – remove rather than updating (default False)
new – return updated rather than original document (default False)
update – Django-style update keyword arguments

no_cache()¶: Convert to a non-caching queryset

no_dereference()¶: Turn off any dereferencing for the results of this queryset.

no_sub_classes()¶

Filter for only the instances of this specific document.

Do NOT return any inherited documents.

none()¶: Returns a queryset that never returns any objects and no query will be executed when accessing the results inspired by django none() https://docs.djangoproject.com/en/dev/ref/models/querysets/#none

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

order_by(*keys)¶

Order the QuerySet by the given keys.

The order may be specified by prepending each of the keys by a “+” or a “-“. Ascending order is assumed if there’s no prefix.

If no keys are passed, existing ordering is cleared instead.

Parameters: keys – fields to order the query results by; keys may be prefixed with “+” or a “-” to determine the ordering direction.

read_concern(read_concern)¶

Change the read_concern when querying.

Parameters: read_concern – override ReplicaSetConnection-level preference.

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.

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.

search_text(text, language=None)¶

Start a text search, using text indexes. Require: MongoDB server version 2.6+.

Parameters: language – The language that determines the list of stop words for the search and the rules for the stemmer and tokenizer. If not specified, the search uses the default language of the index. For supported languages, see Text Search Languages <http://docs.mongodb.org/manual/reference/text-search-languages/#text-search-languages>.

select_related(max_depth=1)¶: Handles dereferencing of DBRef objects or ObjectId a maximum depth in order to cut down the number queries to mongodb.

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

snapshot(enabled)¶

Enable or disable snapshot mode when querying.

Parameters: enabled – whether or not snapshot mode is enabled

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

timeout(enabled)¶

Enable or disable the default mongod timeout when querying. (no_cursor_timeout option)

Parameters: enabled – whether or not the timeout is used

to_json(*args, **kwargs)¶: Converts a queryset to JSON

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

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

Parameters

upsert – insert if document doesn’t exist (default False)
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.
read_concern – Override the read concern for the operation
full_result – Return the associated pymongo.UpdateResult rather than just the number updated items
update – Django-style update keyword arguments

:returns the number of updated documents (unless full_result is True)

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

Perform an atomic update on the fields of the first document matched by the query.

Parameters

upsert – insert if document doesn’t exist (default False)
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 associated pymongo.UpdateResult rather than just the number updated items
update – Django-style update keyword arguments full_result

:returns the number of updated documents (unless full_result is True)

upsert_one(write_concern=None, read_concern=None, **update)¶

Overwrite or add the first document 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.
read_concern – Override the read concern for the operation
update – Django-style update keyword arguments

:returns the new or overwritten document

using(alias)¶

This method is for controlling which database the QuerySet will be evaluated against if you are using more than one database.

Parameters: alias – The database alias

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.

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

class mongoengine.queryset.QuerySetNoCache(document, collection)¶

A non caching QuerySet

__call__(q_obj=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.

query – Django-style query keyword arguments.

cache()¶: Convert to a 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, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, null=False, sparse=False, **kwargs)¶

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.

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

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

A unicode string field.

Parameters

regex – (optional) A string pattern that will be applied during validation
max_length – (optional) A max length that will be applied during validation
min_length – (optional) A min length that will be applied during validation
kwargs – Keyword arguments passed into the parent BaseField

class mongoengine.fields.URLField(url_regex=None, schemes=None, **kwargs)¶

A field that validates input as an URL.

Parameters

url_regex – (optional) Overwrite the default regex used for validation
schemes – (optional) Overwrite the default URL schemes that are allowed
kwargs – Keyword arguments passed into the parent StringField

class mongoengine.fields.EmailField(domain_whitelist=None, allow_utf8_user=False, allow_ip_domain=False, *args, **kwargs)¶

A field that validates input as an email address.

Parameters

domain_whitelist – (optional) list of valid domain names applied during validation
allow_utf8_user – Allow user part of the email to contain utf8 char
allow_ip_domain – Allow domain part of the email to be an IPv4 or IPv6 address
kwargs – Keyword arguments passed into the parent StringField

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

32-bit integer field.

Parameters

min_value – (optional) A min value that will be applied during validation
max_value – (optional) A max value that will be applied during validation
kwargs – Keyword arguments passed into the parent BaseField

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

64-bit integer field. (Equivalent to IntField since the support to Python2 was dropped)

Parameters

min_value – (optional) A min value that will be applied during validation
max_value – (optional) A max value that will be applied during validation
kwargs – Keyword arguments passed into the parent BaseField

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

Floating point number field.

Parameters

min_value – (optional) A min value that will be applied during validation
max_value – (optional) A max value that will be applied during validation
kwargs – Keyword arguments passed into the parent BaseField

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

Fixed-point decimal number field. Stores the value as a float by default unless force_string is used. If using floats, beware of Decimal to float conversion (potential precision loss)

Parameters

min_value – (optional) A min value that will be applied during validation
max_value – (optional) A max value that will be applied during validation
force_string – Store the value as a string (instead of a float). Be aware that this affects query sorting and operation like lte, gte (as string comparison is applied) and some query operator won’t work (e.g. inc, dec)
precision – Number of decimal places to store.
rounding –
The rounding rule from the python decimal library:
- 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
kwargs – Keyword arguments passed into the parent BaseField

class mongoengine.fields.BooleanField(db_field=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, null=False, sparse=False, **kwargs)¶

Boolean field type.

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.DateTimeField(db_field=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, null=False, sparse=False, **kwargs)¶

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 varying types of date formats into valid python datetime objects.

Note: To default the field to the current datetime, use: DateTimeField(default=datetime.utcnow)

Note: Microseconds are rounded to the nearest millisecond.: Pre UTC microsecond support is effectively 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)
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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

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.

Note: To default the field to the current datetime, use: DateTimeField(default=datetime.utcnow)

Parameters

separator – Allows to customize the separator used for storage (default ,)
kwargs – Keyword arguments passed into the parent StringField

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

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

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.GenericEmbeddedDocumentField(db_field=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, null=False, sparse=False, **kwargs)¶

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)
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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.DynamicField(db_field=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, null=False, sparse=False, **kwargs)¶

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)
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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.ListField(field=None, max_length=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 []

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.EmbeddedDocumentListField(document_type, **kwargs)¶

A ListField designed specially to hold a list of embedded documents to provide additional query helpers.

Note

The only valid list values are subclasses of EmbeddedDocument.

Parameters

document_type – The type of EmbeddedDocument the list will hold.
kwargs – Keyword arguments passed into the parent ListField

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.

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.DictField(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 DictFields is {}

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

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.

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

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).

Note this means you will get a database I/O access everytime you access this field. This is necessary because the field returns a Document which precise type can depend of the value of the _cls field present in the document in database. In short, using this type of field can lead to poor performances (especially if you access this field only to retrieve it pk field which is already known before dereference). To solve this you should consider using the LazyReferenceField.

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

The options are:

DO_NOTHING (0) - don’t do anything (default).

NULLIFY (1) - Updates the reference to null.

CASCADE (2) - Deletes the documents associated with the reference.

DENY (3) - Prevent the deletion of the reference object.

PULL (4) - Pull the reference from a ListField of references

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

class Org(Document):
    owner = ReferenceField('User')

class User(Document):
    org = ReferenceField('Org', reverse_delete_rule=CASCADE)

User.register_delete_rule(Org, 'owner', DENY)

Initialises the Reference Field.

Parameters

document_type – The type of Document that will be referenced
dbref – Store the reference as DBRef or as the ObjectId.
reverse_delete_rule – Determines what to do when the referring object is deleted
kwargs – Keyword arguments passed into the parent BaseField

Note

A reference to an abstract document type is always stored as a DBRef, regardless of the value of dbref.

class mongoengine.fields.LazyReferenceField(document_type, passthrough=False, dbref=False, reverse_delete_rule=0, **kwargs)¶

A really lazy reference to a document. Unlike the ReferenceField it will not be automatically (lazily) dereferenced on access. Instead, access will return a LazyReference class instance, allowing access to pk or manual dereference by using fetch() method.

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
passthrough – When trying to access unknown fields, the LazyReference instance will automatically call fetch() and try to retrieve the field on the fetched document. Note this only work getting field (not setting or deleting).

class mongoengine.fields.GenericReferenceField(*args, **kwargs)¶

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

Note this field works the same way as ReferenceField, doing database I/O access the first time it is accessed (even if it’s to access it pk or id field). To solve this you should consider using the GenericLazyReferenceField.

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

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.GenericLazyReferenceField(*args, **kwargs)¶

A reference to any Document subclass. Unlike the GenericReferenceField it will not be automatically (lazily) dereferenced on access. Instead, access will return a LazyReference class instance, allowing access to pk or manual dereference by using fetch() method.

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

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.CachedReferenceField(document_type, fields=None, auto_sync=True, **kwargs)¶

A referencefield with cache fields to purpose pseudo-joins

Initialises the Cached Reference Field.

Parameters

document_type – The type of Document that will be referenced
fields – A list of fields to be cached in document
auto_sync – if True documents are auto updated
kwargs – Keyword arguments passed into the parent BaseField

class mongoengine.fields.BinaryField(max_bytes=None, **kwargs)¶

A binary data field.

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

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

A GridFS storage field.

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

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

A Image File storage field.

Parameters

size – max size to store images, provided as (width, height, force) if larger, it will be automatically resized (ex: size=(800, 600, True))
thumbnail_size – size to generate a thumbnail, provided as (width, height, force)
db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.SequenceField(collection_name=None, db_alias=None, sequence_name=None, value_decorator=None, *args, **kwargs)¶

Provides a sequential counter see:: https://docs.mongodb.com/manual/reference/method/ObjectId/#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.

Parameters

collection_name – Name of the counter collection (default ‘mongoengine.counters’)
sequence_name – Name of the sequence in the collection (default ‘ClassName.counter’)
value_decorator – Any callable to use as a counter (default int)

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.

Note

In case the counter is defined in the abstract document, it will be common to all inherited documents and the default sequence name will be the class name of the abstract document.

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.ObjectIdField(db_field=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, null=False, sparse=False, **kwargs)¶

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)
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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.UUIDField(binary=True, **kwargs)¶

A UUID field.

Store UUID data in the database

Parameters: binary – if False store as a string.

class mongoengine.fields.GeoPointField(db_field=None, required=False, default=None, unique=False, unique_with=None, primary_key=False, validation=None, choices=None, null=False, sparse=False, **kwargs)¶

A list storing a longitude and latitude coordinate.

Note

this represents a generic point in a 2D plane and a legacy way of representing a geo point. It admits 2d indexes but not “2dsphere” indexes in MongoDB > 2.4 which are more natural for modeling geospatial points. See Geospatial indexes

Parameters

db_field – The database field to store this field in (defaults to the name of the 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. The callable takes the value as parameter and should raise a ValidationError if validation fails
choices – (optional) The valid choices
null – (optional) If the field value can be null. If no and there is a default value then the default value is set
sparse – (optional) sparse=True combined with unique=True and required=False means that uniqueness won’t be enforced for None values
**kwargs –
(optional) Arbitrary indirection-free metadata for this field can be supplied as additional keyword arguments and accessed as attributes of the field. Must not conflict with any existing attributes. Common metadata includes verbose_name and help_text.

class mongoengine.fields.PointField(auto_index=True, *args, **kwargs)¶

A GeoJSON field storing a longitude and latitude coordinate.

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

Parameters: auto_index (bool) – Automatically create a ‘2dsphere’ index. Defaults to True.

class mongoengine.fields.LineStringField(auto_index=True, *args, **kwargs)¶

A GeoJSON field storing a line of longitude and latitude coordinates.

The data is represented as:

{'type' : 'LineString' ,
 'coordinates' : [[x1, y1], [x2, y2] ... [xn, yn]]}

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

Requires mongodb >= 2.4

Parameters: auto_index (bool) – Automatically create a ‘2dsphere’ index. Defaults to True.

class mongoengine.fields.PolygonField(auto_index=True, *args, **kwargs)¶

A GeoJSON field storing a polygon of longitude and latitude 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

Parameters: auto_index (bool) – Automatically create a ‘2dsphere’ index. Defaults to True.

class mongoengine.fields.MultiPointField(auto_index=True, *args, **kwargs)¶

A GeoJSON field storing a list of Points.

The data is represented as:

{'type' : 'MultiPoint' ,
 'coordinates' : [[x1, y1], [x2, y2]]}

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

Requires mongodb >= 2.6

Parameters: auto_index (bool) – Automatically create a ‘2dsphere’ index. Defaults to True.

class mongoengine.fields.MultiLineStringField(auto_index=True, *args, **kwargs)¶

A GeoJSON field storing a list of LineStrings.

The data is represented as:

{'type' : 'MultiLineString' ,
 '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 points.

Requires mongodb >= 2.6

Parameters: auto_index (bool) – Automatically create a ‘2dsphere’ index. Defaults to True.

class mongoengine.fields.MultiPolygonField(auto_index=True, *args, **kwargs)¶

A GeoJSON field storing list of Polygons.

The data is represented as:

{'type' : 'MultiPolygon' ,
 'coordinates' : [[
       [[x1, y1], [x1, y1] ... [xn, yn]],
       [[x1, y1], [x1, y1] ... [xn, yn]]
   ], [
       [[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 Polygons.

Requires mongodb >= 2.6

Parameters: auto_index (bool) – 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

class mongoengine.fields.ImageGridFsProxy(grid_id=None, key=None, instance=None, db_alias='default', collection_name='fs')¶: Proxy for ImageField

class mongoengine.fields.ImproperlyConfigured¶

3.6. Embedded Document Querying¶

New in version 0.9.

Additional queries for Embedded Documents are available when using the EmbeddedDocumentListField to store a list of embedded documents.

A list of embedded documents is returned as a special list with the following methods:

class mongoengine.base.datastructures.EmbeddedDocumentList(list_items, instance, name)¶

count()¶

The number of embedded documents in the list.

Returns: The length of the list, equivalent to the result of len().

create(**values)¶

Creates a new instance of the EmbeddedDocument and appends it to this EmbeddedDocumentList.

Note

the instance of the EmbeddedDocument is not automatically saved to the database. You still need to call .save() on the parent Document.

Parameters: values – A dictionary of values for the embedded document.
Returns: The new embedded document instance.

delete()¶

Deletes the embedded documents from the database.

Note

The embedded document changes are not automatically saved to the database after calling this method.

Returns: The number of entries deleted.

exclude(**kwargs)¶

Filters the list by excluding embedded documents with the given keyword arguments.

Parameters: kwargs – The keyword arguments corresponding to the fields to exclude on. Multiple arguments are treated as if they are ANDed together.
Returns: A new EmbeddedDocumentList containing the non-matching embedded documents.

Raises AttributeError if a given keyword is not a valid field for the embedded document class.

filter(**kwargs)¶

Filters the list by only including embedded documents with the given keyword arguments.

This method only supports simple comparison (e.g. .filter(name=’John Doe’)) and does not support operators like __gte, __lte, __icontains like queryset.filter does

Parameters: kwargs – The keyword arguments corresponding to the fields to filter on. Multiple arguments are treated as if they are ANDed together.
Returns: A new EmbeddedDocumentList containing the matching embedded documents.

Raises AttributeError if a given keyword is not a valid field for the embedded document class.

first()¶: Return the first embedded document in the list, or None if empty.

get(**kwargs)¶

Retrieves an embedded document determined by the given keyword arguments.

Parameters: kwargs – The keyword arguments corresponding to the fields to search on. Multiple arguments are treated as if they are ANDed together.
Returns: The embedded document matched by the given keyword arguments.

Raises DoesNotExist if the arguments used to query an embedded document returns no results. MultipleObjectsReturned if more than one result is returned.

save(*args, **kwargs)¶

Saves the ancestor document.

Parameters

args – Arguments passed up to the ancestor Document’s save method.
kwargs – Keyword arguments passed up to the ancestor Document’s save method.

update(**update)¶

Updates the embedded documents with the given replacement values. This function does not support mongoDB update operators such as inc__.

Note

The embedded document changes are not automatically saved to the database after calling this method.

Parameters: update – A dictionary of update values to apply to each embedded document.
Returns: The number of entries updated.

3.7. 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.