53a7bea492
This change removes the u() helper from bson.py3compat and all of its uses in the driver and tests. PyPy3 continues to be supported since, even though it is based on python 3.2.5, it has always supported the u string prefix. The README and install docs are now explicit about PyPy(3) support.
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3.3 KiB
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94 lines
3.3 KiB
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Python 3 FAQ
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============
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.. contents::
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What Python 3 versions are supported?
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-------------------------------------
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PyMongo supports CPython 3.3+ and PyPy3.
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Are there any PyMongo behavior changes with Python 3?
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-----------------------------------------------------
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Only one intentional change. Instances of :class:`bytes`
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are encoded as BSON type 5 (Binary data) with subtype 0.
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In Python 3 they are decoded back to :class:`bytes`. In
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Python 2 they will be decoded to :class:`~bson.binary.Binary`
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with subtype 0.
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For example, let's insert a :class:`bytes` instance using Python 3 then
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read it back. Notice the byte string is decoded back to :class:`bytes`::
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Python 3.3.5 (default, Apr 29 2016, 11:04:32)
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[GCC 4.9.3] on linux
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Type "help", "copyright", "credits" or "license" for more information.
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>>> import pymongo
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>>> c = pymongo.MongoClient()
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>>> c.test.bintest.insert_one({'binary': b'this is a byte string'}).inserted_id
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ObjectId('4f9086b1fba5222021000000')
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>>> c.test.bintest.find_one()
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{'binary': b'this is a byte string', '_id': ObjectId('4f9086b1fba5222021000000')}
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Now retrieve the same document in Python 2. Notice the byte string is decoded
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to :class:`~bson.binary.Binary`::
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Python 2.7.6 (default, Feb 26 2014, 10:36:22)
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[GCC 4.7.3] on linux2
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Type "help", "copyright", "credits" or "license" for more information.
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>>> import pymongo
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>>> c = pymongo.MongoClient()
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>>> c.test.bintest.find_one()
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{u'binary': Binary('this is a byte string', 0), u'_id': ObjectId('4f9086b1fba5222021000000')}
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Why can't I share pickled ObjectIds between some versions of Python 2 and 3?
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----------------------------------------------------------------------------
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Instances of :class:`~bson.objectid.ObjectId` pickled using Python 2
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can always be unpickled using Python 3.
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If you pickled an ObjectId using Python 2 and want to unpickle it using
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Python 3 you must pass ``encoding='latin-1'`` to pickle.loads::
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Python 2.7.6 (default, Feb 26 2014, 10:36:22)
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[GCC 4.7.3] on linux2
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Type "help", "copyright", "credits" or "license" for more information.
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>>> import pickle
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>>> from bson.objectid import ObjectId
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>>> oid = ObjectId()
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>>> oid
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ObjectId('4f919ba2fba5225b84000000')
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>>> pickle.dumps(oid)
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'ccopy_reg\n_reconstructor\np0\n(cbson.objectid\...'
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Python 3.3.5 (default, Apr 29 2016, 11:04:32)
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[GCC 4.9.3] on linux
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Type "help", "copyright", "credits" or "license" for more information.
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>>> import pickle
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>>> pickle.loads(b'ccopy_reg\n_reconstructor\np0\n(cbson.objectid\...', encoding='latin-1')
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ObjectId('4f919ba2fba5225b84000000')
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If you need to pickle ObjectIds using Python 3 and unpickle them using Python 2
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you must use ``protocol <= 2``::
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Python 3.3.5 (default, Apr 29 2016, 11:04:32)
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[GCC 4.9.3] on linux
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Type "help", "copyright", "credits" or "license" for more information.
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>>> import pickle
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>>> from bson.objectid import ObjectId
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>>> oid = ObjectId()
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>>> oid
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ObjectId('4f96f20c430ee6bd06000000')
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>>> pickle.dumps(oid, protocol=2)
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b'\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c_codecs\nencode\...'
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Python 2.6.9 (unknown, Feb 26 2014, 12:39:10)
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[GCC 4.7.3] on linux2
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Type "help", "copyright", "credits" or "license" for more information.
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>>> import pickle
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>>> pickle.loads('\x80\x02cbson.objectid\nObjectId\nq\x00)\x81q\x01c_codecs\nencode\...')
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ObjectId('4f96f20c430ee6bd06000000')
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