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Update the porting HOWTO to be a little less harsh on using 2to3.

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Patch reviewed by Raymond Hettinger, permission from Georg Brandl to commit
during an RC.
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Brett Cannon 2011-02-18 01:34:28 +00:00
parent 8f0ae9a17f
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Doc/howto/pyporting.rst
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@ -31,23 +31,18 @@ If your project is brand-new or does not have a large codebase, then you may
want to consider writing/porting :ref:`all of your code for Python 3 want to consider writing/porting :ref:`all of your code for Python 3
and use 3to2 <use_3to2>` to port your code for Python 2. and use 3to2 <use_3to2>` to port your code for Python 2.
If your project has a pre-existing Python 2 codebase and you would like Python If you would prefer to maintain a codebase which is semantically **and**
3 support to start off a new branch or version of your project, then you will syntactically compatible with Python 2 & 3 simultaneously, you can write
most likely want to :ref:`port using 2to3 <use_2to3>`. This will allow you to :ref:`use_same_source`. While this tends to lead to somewhat non-idiomatic
port your Python 2 code to Python 3 in a semi-automated fashion and begin to code, it does mean you keep a rapid development process for you, the developer.
maintain it separately from your Python 2 code. This approach can also work if
your codebase is small and/or simple enough for the translation to occur
quickly.
Finally, if you want to maintain Python 2 and Python 3 versions of your project Finally, you do have the option of :ref:`using 2to3 <use_2to3>` to translate
simultaneously and with no differences, then you can write :ref:`Python 2/3 Python 2 code into Python 3 code (with some manual help). This can take the
source-compatible code <use_same_source>`. While the code is not quite as form of branching your code and using 2to3 to start a Python 3 branch. You can
idiomatic as it would be written just for Python 3 or automating the port from also have users perform the translation as installation time automatically so
Python 2, it does makes it easier to continue to do rapid development that you only have to maintain a Python 2 codebase.
regardless of what major version of Python you are developing against at the
time.
Regardless of which approach you choose, porting is probably not as hard or Regardless of which approach you choose, porting is not as hard or
time-consuming as you might initially think. You can also tackle the problem time-consuming as you might initially think. You can also tackle the problem
piece-meal as a good portion of porting is simply updating your code to follow piece-meal as a good portion of porting is simply updating your code to follow
current best practices in a Python 2/3 compatible way. current best practices in a Python 2/3 compatible way.
@ -595,7 +590,8 @@ While it may seem counter-intuitive, you can write Python code which is
source-compatible between Python 2 & 3. It does lead to code that is not source-compatible between Python 2 & 3. It does lead to code that is not
entirely idiomatic Python (e.g., having to extract the currently raised entirely idiomatic Python (e.g., having to extract the currently raised
exception from ``sys.exc_info()[1]``), but it can be run under Python 2 exception from ``sys.exc_info()[1]``), but it can be run under Python 2
**and** Python 3 without using 2to3_ as a translation step. This allows you to **and** Python 3 without using 2to3_ as a translation step (although the tool
should be used to help find potential portability problems). This allows you to
continue to have a rapid development process regardless of whether you are continue to have a rapid development process regardless of whether you are
developing under Python 2 or Python 3. Whether this approach or using developing under Python 2 or Python 3. Whether this approach or using
:ref:`use_2to3` works best for you will be a per-project decision. :ref:`use_2to3` works best for you will be a per-project decision.
@ -611,8 +607,8 @@ the same source code.
.. _What's New in Python 3.0: http://docs.python.org/release/3.0/whatsnew/3.0.html .. _What's New in Python 3.0: http://docs.python.org/release/3.0/whatsnew/3.0.html
Follow The Steps for Using 2to3_ (sans 2to3) Follow The Steps for Using 2to3_
-------------------------------------------- --------------------------------
All of the steps outlined in how to All of the steps outlined in how to
:ref:`port Python 2 code with 2to3 <use_2to3>` apply :ref:`port Python 2 code with 2to3 <use_2to3>` apply
@ -689,10 +685,11 @@ likely don't need it.
Other Resources Other Resources
=============== ===============
The authors of the following blog posts and wiki pages deserve special thanks The authors of the following blog posts, wiki pages, and books deserve special
for making public their tips for porting Python 2 code to Python 3 (and thus thanks for making public their tips for porting Python 2 code to Python 3 (and
helping provide information for this document): thus helping provide information for this document):
* http://python3porting.com/
* http://docs.pythonsprints.com/python3_porting/py-porting.html * http://docs.pythonsprints.com/python3_porting/py-porting.html
* http://techspot.zzzeek.org/2011/01/24/zzzeek-s-guide-to-python-3-porting/ * http://techspot.zzzeek.org/2011/01/24/zzzeek-s-guide-to-python-3-porting/
* http://dabeaz.blogspot.com/2011/01/porting-py65-and-my-superboard-to.html * http://dabeaz.blogspot.com/2011/01/porting-py65-and-my-superboard-to.html