d2cde8719a
If you need to continue to use any of these Python versions with MongoDB the 2.x branch of PyMongo will continue to be minimally maintained for some time.
173 lines
6.7 KiB
ReStructuredText
173 lines
6.7 KiB
ReStructuredText
Python 3 FAQ
|
|
============
|
|
|
|
.. contents::
|
|
|
|
What Python 3 versions are supported?
|
|
-------------------------------------
|
|
|
|
PyMongo supports Python 3.x where x >= 2.
|
|
|
|
Are there any PyMongo behavior changes with Python 3?
|
|
-----------------------------------------------------
|
|
|
|
Only one intentional change. Instances of :class:`bytes`
|
|
are encoded as BSON type 5 (Binary data) with subtype 0.
|
|
In Python 3 they are decoded back to :class:`bytes`. In
|
|
Python 2 they will be decoded to :class:`~bson.binary.Binary`
|
|
with subtype 0.
|
|
|
|
For example, let's insert a :class:`bytes` instance using Python 3 then
|
|
read it back. Notice the byte string is decoded back to :class:`bytes`::
|
|
|
|
Python 3.2.5 (default, Feb 26 2014, 12:40:25)
|
|
[GCC 4.7.3] on linux2
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pymongo
|
|
>>> c = pymongo.MongoClient()
|
|
>>> c.test.bintest.insert({'binary': b'this is a byte string'})
|
|
ObjectId('4f9086b1fba5222021000000')
|
|
>>> c.test.bintest.find_one()
|
|
{'binary': b'this is a byte string', '_id': ObjectId('4f9086b1fba5222021000000')}
|
|
|
|
Now retrieve the same document in Python 2. Notice the byte string is decoded
|
|
to :class:`~bson.binary.Binary`::
|
|
|
|
Python 2.7.6 (default, Feb 26 2014, 10:36:22)
|
|
[GCC 4.7.3] on linux2
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pymongo
|
|
>>> c = pymongo.MongoClient()
|
|
>>> c.test.bintest.find_one()
|
|
{u'binary': Binary('this is a byte string', 0), u'_id': ObjectId('4f9086b1fba5222021000000')}
|
|
|
|
|
|
Why can't I share pickled ObjectIds between some versions of Python 2 and 3?
|
|
----------------------------------------------------------------------------
|
|
|
|
Instances of :class:`~bson.objectid.ObjectId` pickled using Python 2
|
|
can always be unpickled using Python 3. Due to
|
|
`http://bugs.python.org/issue13505 <http://bugs.python.org/issue13505>`_
|
|
you must use Python 3.2.3 or newer to pickle instances of ObjectId if you
|
|
need to unpickle them in Python 2.
|
|
|
|
If you pickled an ObjectId using Python 2 and want to unpickle it using
|
|
Python 3 you must pass ``encoding='latin-1'`` to pickle.loads::
|
|
|
|
Python 2.7.6 (default, Feb 26 2014, 10:36:22)
|
|
[GCC 4.7.3] on linux2
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pickle
|
|
>>> from bson.objectid import ObjectId
|
|
>>> oid = ObjectId()
|
|
>>> oid
|
|
ObjectId('4f919ba2fba5225b84000000')
|
|
>>> pickle.dumps(oid)
|
|
'ccopy_reg\n_reconstructor\np0\n(cbson.objectid\...'
|
|
|
|
Python 3.2.5 (default, Feb 26 2014, 12:40:25)
|
|
[GCC 4.7.3] on linux2
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pickle
|
|
>>> pickle.loads(b'ccopy_reg\n_reconstructor\np0\n(cbson.objectid\...', encoding='latin-1')
|
|
ObjectId('4f919ba2fba5225b84000000')
|
|
|
|
|
|
If you need to pickle ObjectIds using Python 3 and unpickle them using Python 2
|
|
you must use Python 3.2.3 or newer and ``protocol <= 2``::
|
|
|
|
Python 3.2.3 (v3.2.3:3d0686d90f55, Apr 10 2012, 11:25:50)
|
|
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pickle
|
|
>>> from bson.objectid import ObjectId
|
|
>>> oid = ObjectId()
|
|
>>> oid
|
|
ObjectId('4f96f20c430ee6bd06000000')
|
|
>>> pickle.dumps(oid, protocol=2)
|
|
b'\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c_codecs\nencode\...'
|
|
|
|
Python 2.6.9 (unknown, Feb 26 2014, 12:39:10)
|
|
[GCC 4.7.3] on linux2
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pickle
|
|
>>> pickle.loads('\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c_codecs\nencode\...')
|
|
ObjectId('4f96f20c430ee6bd06000000')
|
|
|
|
|
|
Unfortunately this won't work if you pickled the ObjectId using a Python 3
|
|
version older than 3.2.3::
|
|
|
|
Python 3.2.2 (default, Mar 21 2012, 14:32:23)
|
|
[GCC 4.5.3] on linux2
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pickle
|
|
>>> from bson.objectid import ObjectId
|
|
>>> oid = ObjectId()
|
|
>>> pickle.dumps(oid, protocol=2)
|
|
b'\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c__builtin__\nbytes\...'
|
|
|
|
Python 2.4.6 (#1, Apr 12 2012, 14:48:24)
|
|
[GCC 4.5.3] on linux3
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pickle
|
|
>>> pickle.loads('\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c__builtin__\nbytes\...')
|
|
Traceback (most recent call last):
|
|
File "<stdin>", line 1, in ?
|
|
File "/usr/lib/python2.4/pickle.py", line 1394, in loads
|
|
return Unpickler(file).load()
|
|
File "/usr/lib/python2.4/pickle.py", line 872, in load
|
|
dispatch[key](self)
|
|
File "/usr/lib/python2.4/pickle.py", line 1104, in load_global
|
|
klass = self.find_class(module, name)
|
|
File "/usr/lib/python2.4/pickle.py", line 1140, in find_class
|
|
klass = getattr(mod, name)
|
|
AttributeError: 'module' object has no attribute 'bytes'
|
|
|
|
.. warning::
|
|
|
|
Unpickling in Python 2.6 or 2.7 an ObjectId pickled in a Python 3 version
|
|
older than 3.2.3 will seem to succeed but the resulting ObjectId instance
|
|
will contain garbage data.
|
|
|
|
>>> pickle.loads('\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c__builtin__\nbytes\...)
|
|
ObjectId('5b37392c203135302c203234362c2034352c203235312c203136352c2033342c203532...')
|
|
|
|
|
|
Why do I get a syntax error importing pymongo after installing from source?
|
|
---------------------------------------------------------------------------
|
|
|
|
PyMongo makes use of the 2to3 tool to translate much of its code to valid
|
|
Python 3 syntax at install time. The translated modules are written to the
|
|
build subdirectory before being installed, leaving the original source files
|
|
intact. If you start the python interactive shell from the top level source
|
|
directory after running ``python setup.py install`` the untranslated modules
|
|
will be the first thing in your path. Importing pymongo will result in an
|
|
exception similar to::
|
|
|
|
Python 3.2.5 (default, Feb 26 2014, 12:40:25)
|
|
[GCC 4.7.3] on linux2
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pymongo
|
|
Traceback (most recent call last):
|
|
File "<stdin>", line 1, in <module>
|
|
File "pymongo/__init__.py", line 77, in <module>
|
|
version = get_version_string()
|
|
File "pymongo/__init__.py", line 73, in get_version_string
|
|
if isinstance(version_tuple[-1], basestring):
|
|
NameError: global name 'basestring' is not defined
|
|
|
|
Note the path in the traceback (``pymongo/__init__.py``). Changing out of the
|
|
source directory takes the untranslated modules out of your path::
|
|
|
|
$ cd ..
|
|
$ python
|
|
Python 3.2.5 (default, Feb 26 2014, 12:40:25)
|
|
[GCC 4.7.3] on linux2
|
|
Type "help", "copyright", "credits" or "license" for more information.
|
|
>>> import pymongo
|
|
>>> pymongo.__file__
|
|
'/home/behackett/py3k/lib/python3.2/site-packages/pymongo-2.7-py3.2-linux-x86_64.egg/pymongo/__init__.py'
|
|
|
|
|