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Make the case to only support Python 2.7 when supporting 2/3 simultaneously

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Brett Cannon 2015-03-13 12:49:44 -04:00
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Doc/howto/pyporting.rst
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@ -28,15 +28,14 @@ The Short Explanation
To make your project be single-source Python 2/3 compatible, the basic steps
are:
#. Update your code to drop support for Python 2.5 or older (supporting only
Python 2.7 is ideal)
#. Only worry about supporting Python 2.7
#. Make sure you have good test coverage (coverage.py_ can help;
``pip install coverage``)
#. Learn the differences between Python 2 & 3
#. Use Modernize_ or Futurize_ to update your code (``pip install modernize`` or
``pip install future``, respectively)
#. Use Pylint_ to help make sure you don't regress on your Python 3 support
(if only supporting Python 2.7/3.4 or newer; ``pip install pylint``)
(``pip install pylint``)
#. Use caniusepython3_ to find out which of your dependencies are blocking your
use of Python 3 (``pip install caniusepython3``)
#. Once your dependencies are no longer blocking you, use continuous integration
@ -67,26 +66,27 @@ Keep those key points in mind while you read on about the details of porting
your code to support Python 2 & 3 simultaneously.
Drop support for Python 2.5 and older (at least)
------------------------------------------------
Drop support for Python 2.6 and older
-------------------------------------
While you can make Python 2.5 work with Python 3, it is **much** easier if you
only have to work with Python 2.6 or newer (and easier still if you only have
to work with Python 2.7). If dropping Python 2.5 is not an option then the six_
project can help you support Python 2.5 & 3 simultaneously
only have to work with Python 2.7. If dropping Python 2.5 is not an
option then the six_ project can help you support Python 2.5 & 3 simultaneously
(``pip install six``). Do realize, though, that nearly all the projects listed
in this HOWTO will not be available to you.
If you are able to only support Python 2.6 or newer, then the required changes
If you are able to skip Python 2.5 and older, then the required changes
to your code should continue to look and feel like idiomatic Python code. At
worst you will have to use a function instead of a method in some instances or
have to import a function instead of using a built-in one, but otherwise the
overall transformation should not feel foreign to you.
But please aim for Python 2.7. Bugfixes for that version of Python will continue
until 2020 while Python 2.6 is no longer supported. There are also some tools
mentioned in this HOWTO which do not support Python 2.6 (e.g., Pylint_), and
this will become more commonplace as time goes on.
But you should aim for only supporting Python 2.7. Python 2.6 is no longer
supported and thus is not receiving bugfixes. This means **you** will have to
work around any issues you come across with Python 2.6. There are also some
tools mentioned in this HOWTO which do not support Python 2.6 (e.g., Pylint_),
and this will become more commonplace as time goes on. It will simply be easier
for you if you only support the versions of Python that you have to support.
Make sure you specify the proper version support in your ``setup.py`` file
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