Python 3 FAQ

    Only one intentional change. Instances of are encoded as BSON type 5 (Binary data) with subtype 0.In Python 3 they are decoded back to bytes. InPython 2 they are decoded to with subtype 0.

    For example, let’s insert a bytes instance using Python 3 thenread it back. Notice the byte string is decoded back to :

    1. Python 2.7.6 (default, Feb 26 2014, 10:36:22)
    2. [GCC 4.7.3] on linux2
    3. Type "help", "copyright", "credits" or "license" for more information.
    4. >>> import pymongo
    5. >>> c = pymongo.MongoClient()
    6. >>> c.test.bintest.find_one()
    7. {u'binary': Binary('this is a byte string', 0), u'_id': ObjectId('4f9086b1fba5222021000000')}

    There is a similar change in behavior in parsing JSON binary with subtype 0.In Python 3 they are decoded into bytes. In Python 2 they aredecoded to with subtype 0.

    For example, let’s decode a JSON binary subtype 0 using Python 3. Notice thebyte string is decoded to :

    1. [GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
    2. Type "help", "copyright", "credits" or "license" for more information.
    3. >>> from bson.json_util import loads
    4. >>> loads('{"b": {"$binary": "dGhpcyBpcyBhIGJ5dGUgc3RyaW5n", "$type": "00"}}')
    5. {u'b': Binary('this is a byte string', 0)}

    Instances of pickled using Python 2can always be unpickled using Python 3.

    If you pickled an ObjectId using Python 2 and want to unpickle it usingPython 3 you must pass encoding='latin-1' to pickle.loads:

    1. Python 3.6.5 (default, Jun 21 2018, 15:09:09)
    2. [GCC 7.3.0] on linux
    3. Type "help", "copyright", "credits" or "license" for more information.
    4. >>> import pickle
    5. >>> from bson.objectid import ObjectId
    6. >>> oid
    7. ObjectId('4f96f20c430ee6bd06000000')
    8. >>> pickle.dumps(oid, protocol=2)
    9. b'\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c_codecs\nencode\...'
    10.  
    11. Python 2.7.15 (default, Jun 21 2018, 15:00:48)
    12. [GCC 7.3.0] on linux2
    13. Type "help", "copyright", "credits" or "license" for more information.
    14. >>> import pickle
    15. >>> pickle.loads('\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c_codecs\nencode\...')