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