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limitations of the ``future`` module and differences between Py2 and Py3 that are not (yet) handled
===================================================================================================
The following attributes on functions in Python 3 are not provided in Python
2.7:
__func__: see six.get_method_function()
__self__: see six.get_method_self()
__self__.__class__
Limitations of the ``futurize`` script
--------------------------------------
The ``futurize`` script is not yet mature; like ``2to3``, on which it is based,
it makes mistakes. Nevertheless, it should be useful for automatically
performing a lot of the repetitive code-substitution tasks when porting from
Py2 to Py2/3.
Some new Python 3.3 features that cause SyntaxErrors on earlier versions
are not currently handled by the ``futurize`` script. This includes:
- ``yield ... from`` syntax for generators in Py3.3
- ``raise ... from`` syntax for exceptions. (This is simple to fix
manually by creating a temporary variable.)
Also:
- Usage of ``file('myfile', 'w')`` as a synonym for ``open`` doesn't seem
to be converted currently.
- ``isinstance(var, basestring)`` should sometimes be converted to
``isinstance(var, str) or isinstance(var, bytes)``, or sometimes simply
``isinstance(var, str)``, depending on the context. Currently it is always
converted to ``isinstance(var, str)``.
- Caveats with bytes indexing!::
b'\x00'[0] != 0
b'\x01'[0] != 1
``futurize`` does not yet wrap all byte-string literals in a ``bytes()``
call. This is on the to-do list. See :ref:`bytes-object` for more information.
Notes
-----
- Ensure you are using new-style classes on Py2. Py3 doesn't require
inheritance from ``object`` for this, but Py2 does. ``pasteurize``
adds this back in automatically, but ensure you do this too
when writing your classes, otherwise weird breakage when e.g. calling
``super()`` may occur.
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