diff options
Diffstat (limited to 'Doc/whatsnew')
| -rw-r--r-- | Doc/whatsnew/3.1.rst | 42 |
1 files changed, 24 insertions, 18 deletions
diff --git a/Doc/whatsnew/3.1.rst b/Doc/whatsnew/3.1.rst index e560bcd..290cd5c 100644 --- a/Doc/whatsnew/3.1.rst +++ b/Doc/whatsnew/3.1.rst @@ -376,6 +376,30 @@ New, Improved, and Deprecated Modules (Contributed by Derek Morr; :issue:`1655` and :issue:`1664`.) +* The :mod:`pickle` module has been adapted for better interoperability with + Python 2.x when used with protocol 2 or lower. The reorganization of the + standard library changed the formal reference for many objects. For + example, ``__builtin__.set`` in Python 2 is called ``builtins.set`` in Python + 3. This change cofounded efforts to share data between different versions of + Python. But now when protocol 2 or lower is selected, the pickler will + automatically use the old Python 2 names for both loading and dumping. This + remapping is turned-on by default but can be disabled with the *fix_imports* + option:: + + >>> s = {1, 2, 3} + >>> pickle.dumps(s, protocol=0) + b'c__builtin__\nset\np0\n((lp1\nL1L\naL2L\naL3L\natp2\nRp3\n.' + >>> pickle.dumps(s, protocol=0, fix_imports=False) + b'cbuiltins\nset\np0\n((lp1\nL1L\naL2L\naL3L\natp2\nRp3\n.' + + An unfortunate but unavoidable side-effect of this change is that protocol 2 + pickles produced by Python 3.1 won't be readable with Python 3.0. The latest + pickle protocol, protocol 3, should be used when migrating data between + Python 3.x implementations, as it doesn't attempt to remain compatible with + Python 2.x. + + (Contributed by Alexandre Vassalotti and Antoine Pitrou, :issue:`6137`.) + * A new module, :mod:`importlib` was added. It provides a complete, portable, pure Python reference implementation of the :keyword:`import` statement and its counterpart, the :func:`__import__` function. It represents a substantial @@ -384,24 +408,6 @@ New, Improved, and Deprecated Modules (Contributed by Brett Cannon.) -* :mod:`pickle` is now more compatible with Python 2.x when using a - 2.x-compatible protocol (that is, protocol 2 or lower), through translation - of some standard library module names to or from their Python 2.x - equivalents. - - This means that more (protocol 2 or lower) pickles produced by Python 3.1 - will be reusable by Python 2.x, and vice-versa. Standard set objects are - an example of this improvement. - - This has the (unfortunate but unavoidable) side effect that some - protocol 2 pickles produced by Python 3.1 won't be readable with - Python 3.0. The latest pickle protocol, protocol 3, should be used when - migrating data between Python 3.x implementations, as it doesn't attempt - to remain compatible with Python 2.x. - - (Contributed by Alexandre Vassalotti and Antoine Pitrou, :issue:`6137`.) - - Optimizations ============= |