Skip to main content
Join the official 2020 Python Developers SurveyStart the survey!

Fork of Python 3 pickle module.

Project description

ZODB Pickle

This package is a fork of Python 3.3’s pickle module, including its C optimizations. There are several changes so that ZODBs can be used using Python 2 and Python 3 code.

Loading/Storing Python 2 Strings

In all their wisdom, the Python developers have decided that Python 2 str instances should be loaded as Python 3 str objects (i.e. unicode strings). Patches were proposed in Python issue 6784 but were never applied. This code base contains those patches.

Example 1: Loading Python 2 pickles on Python 3

$ python2
>>> import pickle
>>> pickle.dumps('\xff', protocol=0)
"S'\\xff'\np0\n."
>>> pickle.dumps('\xff', protocol=1)
'U\x01\xffq\x00.'
>>> pickle.dumps('\xff', protocol=2)
'\x80\x02U\x01\xffq\x00.'

$ python3
>>> from zodbpickle import pickle
>>> pickle.loads(b"S'\\xff'\np0\n.", encoding='bytes')
b'\xff'
>>> pickle.loads(b'U\x01\xffq\x00.', encoding='bytes')
b'\xff'
>>> pickle.loads(b'\x80\x02U\x01\xffq\x00.', encoding='bytes')
b'\xff'

Example 2: Loading Python 3 pickles on Python 2

$ python3
>>> from zodbpickle import pickle
>>> pickle.dumps(b"\xff", protocol=0)
b'c_codecs\nencode\np0\n(V\xff\np1\nVlatin1\np2\ntp3\nRp4\n.'
>>> pickle.dumps(b"\xff", protocol=1)
b'c_codecs\nencode\nq\x00(X\x02\x00\x00\x00\xc3\xbfq\x01X\x06\x00\x00\x00latin1q\x02tq\x03Rq\x04.'
>>> pickle.dumps(b"\xff", protocol=2)
b'\x80\x02c_codecs\nencode\nq\x00X\x02\x00\x00\x00\xc3\xbfq\x01X\x06\x00\x00\x00latin1q\x02\x86q\x03Rq\x04.'

$ python2
>>> import pickle
>>> pickle.loads('c_codecs\nencode\np0\n(V\xff\np1\nVlatin1\np2\ntp3\nRp4\n.')
'\xff'
>>> pickle.loads('c_codecs\nencode\nq\x00(X\x02\x00\x00\x00\xc3\xbfq\x01X\x06\x00\x00\x00latin1q\x02tq\x03Rq\x04.')
'\xff'
>>> pickle.loads('\x80\x02c_codecs\nencode\nq\x00X\x02\x00\x00\x00\xc3\xbfq\x01X\x06\x00\x00\x00latin1q\x02\x86q\x03Rq\x04.')
'\xff'

Example 3: everything breaks down

$ python2
>>> class Foo(object):
...     def __init__(self):
...         self.x = 'hello'
...
>>> import pickle
>>> pickle.dumps(Foo(), protocol=0)
"ccopy_reg\n_reconstructor\np0\n(c__main__\nFoo\np1\nc__builtin__\nobject\np2\nNtp3\nRp4\n(dp5\nS'x'\np6\nS'hello'\np7\nsb."
>>> pickle.dumps(Foo(), protocol=1)
'ccopy_reg\n_reconstructor\nq\x00(c__main__\nFoo\nq\x01c__builtin__\nobject\nq\x02Ntq\x03Rq\x04}q\x05U\x01xq\x06U\x05helloq\x07sb.'
>>> pickle.dumps(Foo(), protocol=2)
'\x80\x02c__main__\nFoo\nq\x00)\x81q\x01}q\x02U\x01xq\x03U\x05helloq\x04sb.'

$ python3
>>> from zodbpickle import pickle
>>> class Foo(object): pass
...
>>> foo = pickle.loads("ccopy_reg\n_reconstructor\np0\n(c__main__\nFoo\np1\nc__builtin__\nobject\np2\nNtp3\nRp4\n(dp5\nS'x'\np6\nS'hello'\np7\nsb.", encoding='bytes')
>>> foo.x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Foo' object has no attribute 'x'

wait what?

>>> foo.__dict__
{b'x': b'hello'}

oooh. So we use encoding='ASCII' (the default) and errors='bytes' and hope it works:

>>> foo = pickle.loads("ccopy_reg\n_reconstructor\np0\n(c__main__\nFoo\np1\nc__builtin__\nobject\np2\nNtp3\nRp4\n(dp5\nS'x'\np6\nS'hello'\np7\nsb.", errors='bytes')
>>> foo.x
'hello'

falling back to bytes if necessary

>>> pickle.loads(b'\x80\x02U\x01\xffq\x00.', errors='bytes')
b'\xff'

Support for noload()

The ZODB uses cPickle’s noload() method to retrieve all persistent references from a pickle without loading any objects. This feature was removed from Python 3’s pickle. Unfortuantely, this unnecessarily fills the pickle cache.

This module provides a noload() method again.

CHANGES

0.1.0 (2013-02-27)

  • Initial release of Python 3.3’s pickle with the patches of Python issue 6784 applied.
  • Added support for errors="bytes".

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for zodbpickle, version 0.1.0
Filename, size File type Python version Upload date Hashes
Filename, size zodbpickle-0.1.0.tar.gz (96.0 kB) File type Source Python version None Upload date Hashes View

Supported by

Pingdom Pingdom Monitoring Google Google Object Storage and Download Analytics Sentry Sentry Error logging AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN DigiCert DigiCert EV certificate StatusPage StatusPage Status page