Installing System Requirements
==============================

The ``argparse`` package requires that a Python interpreter be installed with
the ``argparse`` and ``json`` (or ``simplejson``) modules.  They are
automatically included with recent Python implementations starting with versions
2.7 and 3.2.  The package will not install Python for you and ``ArgumentParser``
will throw an error if it can not find a sufficient Python interpreter.  This
package is tested with the traditional implementation of Python aka CPython
(either 2.7 or 3.2+ is fine) but probably works with other implementations (for
example it has been lightly tested to work with PyPy).  If you are using Linux
or a Mac you probably already have CPython installed but it might be too old and
you might want to upgrade using your distribution package manager.  For more
information on installing Python go to:

    http://www.python.org/download/

If you have Python 2.7 or 3.2 and higher the ``argparse`` and ``json`` modules
are part of the standard library and should be automatically installed with the
installation of the Python interpreter.  If you have less than Python 2.7 you
should probably upgrade or have your administrator do so.  You can also have
Python 2.7 installed alongside the older Python (as the binary ``python2.7``)

However, if you have Python 2.6, Python 3.1, or Python 3.0 you you should be
able to get by if you install the ``argparse`` module yourself:

    https://code.google.com/p/argparse/  

If you have Python 2.5 in addition to installing the ``argparse`` module you
will need to install the ``simplejson`` module as well:

    https://github.com/simplejson/simplejson

Support for Non-ASCII characters
================================

If you want to use Unicode arguments with ``argparse`` 
you'll need to use Python 3.0+ instead of Python 2.5-2.7.
You'll probably also need to use a terminal and/or shell that supports Unicode.

Having ``argparse`` find Python
===============================

You may specify the Python interpreter for ``argparse`` to use by either setting
the ``python_cmd`` option::

    options(python_cmd = "D:/NonstandardWindowsInstallation/Python27/python")

or by passing the path to the ``python_cmd`` argument in the ``ArgumentParser``
function::

    ArgumentParser(description="A simple Rscript", python_cmd="pypy")

If these are not specified then by default ``ArgumentParser`` will 
use the package ``findpython`` to look for a suitable Python binary.