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Cea Stapleton
102 lines
3.6 KiB
ReStructuredText
102 lines
3.6 KiB
ReStructuredText
Picking an Interpreter
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======================
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.. _which-python:
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Today (Python 2)
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~~~~~~~~~~~~~~~~
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If you're choosing a Python interpreter to use, I *highly* recommend you use
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Python 2.7.x, unless you have a strong reason not to.
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Also use Python 2.7.x if you're starting to work on a new Python module. If you
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have managed to get it working on 2.7, you can add support for older 2.x
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versions.
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The Future (Python 3)
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~~~~~~~~~~~~~~~~~~~~~
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Python 2.x is the status quo, Python 3.x is the shiny new thing.
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`Further Reading <http://wiki.python.org/moin/Python2orPython3>`_
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The difference between Python 3 and Python 2 is much greater, therefore
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writing code that works in both Python 2 and Python 3 is a very complicated
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process.
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It is possible to `write code that works on Python 2.6, 2.7 and 3.3
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<http://lucumr.pocoo.org/2013/5/21/porting-to-python-3-redux/>`_. This
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ranges from tricky to extremely hard depending upon the kind of software
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you are writing; if you're a beginner there are far more important things to
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worry about.
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Implementations
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~~~~~~~~~~~~~~~
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When people speak of *Python* they often mean not just the language but also
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the CPython implementation. *Python* is actually a specification for a language
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that can be implemented in many different ways.
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CPython
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-------
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`CPython <http://www.python.org>`_ is the reference implementation of Python,
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written in C. It compiles Python code to intermediate bytecode which is then
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interpreted by a virtual machine. CPython provides the highest
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level of compatibility with Python packages and C extension modules.
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If you are writing open-source Python code and want to reach the widest possible
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audience, targeting CPython is best. To use packages which rely on C extensions
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to function, CPython is your only implementation option.
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All versions of the Python language are implemented in C because CPython is the
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reference implementation.
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PyPy
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----
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`PyPy <http://pypy.org/>`_ is a Python interpreter implemented in a restricted
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statically-typed subset of the Python language called RPython. The interpreter
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features a just-in-time compiler and supports multiple back-ends (C, CLI, JVM).
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PyPy aims for maximum compatibility with the reference CPython implementation
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while improving performance.
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If you are looking to increase performance of your Python code, it's
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worth giving PyPy a try. On a suite of benchmarks, it's currently `over 5 times
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faster than CPython <http://speed.pypy.org/>`_.
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PyPy supports Python 2.7. PyPy3 [#pypy_ver]_, released in beta, targets Python 3.
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Jython
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------
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`Jython <http://www.jython.org/>`_ is a Python implementation that compiles
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Python code to Java bytecode which is then executed by the JVM (Java Virtual Machine).
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Additionally, it is able to import and use any Java class like a Python
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module.
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If you need to interface with an existing Java codebase or have other reasons to
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need to write Python code for the JVM, Jython is the best choice.
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Jython currently supports up to Python 2.5. [#jython_ver]_
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IronPython
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----------
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`IronPython <http://ironpython.net/>`_ is an implementation of Python for the .NET
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framework. It can use both Python and .NET framework libraries, and can also
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expose Python code to other languages in the .NET framework.
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`Python Tools for Visual Studio <http://ironpython.net/tools/>`_ integrates
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IronPython directly into the Visual Studio development environment, making it
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an ideal choice for Windows developers.
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IronPython supports Python 2.7. [#iron_ver]_
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.. [#pypy_ver] http://pypy.org/compat.html
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.. [#jython_ver] http://wiki.python.org/jython/JythonFaq/GeneralInfo#Is_Jython_the_same_language_as_Python.3F
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.. [#iron_ver] http://ironpython.codeplex.com/releases/view/81726
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