objectid – Tools for working with MongoDB ObjectIds

Tools for working with MongoDB ObjectIds.

class bson.objectid.ObjectId(oid=None)

Initialize a new ObjectId.

An ObjectId is a 12-byte unique identifier consisting of:

  • a 4-byte value representing the seconds since the Unix epoch,
  • a 3-byte machine identifier,
  • a 2-byte process id, and
  • a 3-byte counter, starting with a random value.

By default, ObjectId() creates a new unique identifier. The optional parameter oid can be an ObjectId, or any 12 bytes or, in Python 2, any 12-character str.

For example, the 12 bytes b’foo-bar-quux’ do not follow the ObjectId specification but they are acceptable input:

>>> ObjectId(b'foo-bar-quux')

oid can also be a unicode or str of 24 hex digits:

>>> ObjectId('0123456789ab0123456789ab')
>>> # A u-prefixed unicode literal:
>>> ObjectId(u'0123456789ab0123456789ab')

Raises InvalidId if oid is not 12 bytes nor 24 hex digits, or TypeError if oid is not an accepted type.

  • oid (optional): a valid ObjectId.

See also

The MongoDB documentation on



Get a hex encoded version of ObjectId o.

The following property always holds:

>>> o = ObjectId()
>>> o == ObjectId(str(o))

This representation is useful for urls or other places where o.binary is inappropriate.


12-byte binary representation of this ObjectId.

classmethod from_datetime(generation_time)

Create a dummy ObjectId instance with a specific generation time.

This method is useful for doing range queries on a field containing ObjectId instances.


It is not safe to insert a document containing an ObjectId generated using this method. This method deliberately eliminates the uniqueness guarantee that ObjectIds generally provide. ObjectIds generated with this method should be used exclusively in queries.

generation_time will be converted to UTC. Naive datetime instances will be treated as though they already contain UTC.

An example using this helper to get documents where "_id" was generated before January 1, 2010 would be:

>>> gen_time = datetime.datetime(2010, 1, 1)
>>> dummy_id = ObjectId.from_datetime(gen_time)
>>> result = collection.find({"_id": {"$lt": dummy_id}})
  • generation_time: datetime to be used as the generation time for the resulting ObjectId.

A datetime.datetime instance representing the time of generation for this ObjectId.

The datetime.datetime is timezone aware, and represents the generation time in UTC. It is precise to the second.

classmethod is_valid(oid)

Checks if a oid string is valid or not.

  • oid: the object id to validate

New in version 2.3.