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= How to run Sage in a systemwide Python =

Ondrej wrote this wiki page, but please read this important statement from Michael:

'''Important''': One should note that this can cause various problems due to different python build options. Currently the script below does not work on OSX since Apple's Python is compiled with ucs2 while Sage's Python is compiled with ucs4. Once you compile Sage's Python with ucs2 you will then have the problem that Apple's Python is universal and build with different options than Sage's Python. The upcoming 64 bit Sage will not work at all unless Apple upgrades its Python in OSX 10.6 to be also universal in 64 bit mode. If you encounter any bug or problem please state clearly that you are using the system's python since that configuration might contribute to the problem. The Sage people will attempt to reproduce the problem with vanilla Sage, but because there are a large number of distributions out there we cannot debug problems where we might not have access, so if you break Sage that way you get to keep the pieces ;-). That being said we encourage you to experiment with Sage and use it from your system's Python, we just need to know if anything goes wrong.

     Michael Abshoff, Release Manager of Sage

== Easy Way ==
Create this `s.py` python script:

{{{
#!python
import os
import re
import sys
def set_paths(root="/home/ondra/ext/sage"):
    """
    Set paths necessary to import sage.
    root ... the path to your Sage installation
    """
    python_path = [
        root+"/local/lib/python",
        root+"/local/lib/python2.5/lib-dynload",
        root+"/local/lib/python2.5/site-packages",
            ]
    sys.path = python_path + sys.path
    paths = {
            "SAGE_ROOT": root,
            "SAGE_LOCAL": root+"/local",
            "DOT_SAGE": "~/.sage/",
            "SAGE_SERVER": "http://www.sagemath.org/",
            "PATH": root+"/local/bin:"+os.environ["PATH"],
            }
    os.environ.update(paths)
def import_sageall():
    """
    Imports sage by "import sage.all".
    If it fails, write a helpful message and exit. After executing this method,
    you can be sure that sage just works, e.g you can do
    from sage.all import something
    without worrying.
    """
    try:
        import sage.all
    except ImportError, e:
        if re.match("(.*).so: cannot open shared object file: No such file or directory", e.message):
            # all seems to be just a LD_LIBRARY_PATH problem in 99% of cases
            print """\
"import sage.all" failed when importing an .so library, this is most probably
an LD_LIBRARY_PATH problem, please set your LD_LIBRARY_PATH and try again, e.g. execute:
LD_LIBRARY_PATH=%s/local/lib python %s""" % (os.environ.get("SAGE_ROOT", ""),
        sys.argv[0])
            sys.exit()
        else:
            # some other problem
            raise
set_paths()
import_sageall()
from sage.all import *
var("x")
e = x**2/3-log(x)
print e
print integrate(e, x)
}}}
and try to run it:

{{{
$ python s.py
"import sage.all" failed when importing an .so library, this is most probably
an LD_LIBRARY_PATH problem, please set your LD_LIBRARY_PATH and try again, e.g. execute:
LD_LIBRARY_PATH=/home/ondra/ext/sage/local/lib python s.py
}}}
it tells you the exact command that you need to execute to make it work, so do it:

{{{
$ LD_LIBRARY_PATH=/home/ondra/ext/sage/local/lib python s.py
                                   2
                                  x
                                  -- - log(x)
                                  3
                                            3
                                           x
                              - x log(x) + -- + x
                                           9
}}}
So as you can see from the above, all you have to do is to set the `root` keyword parameter in the script to point to your Sage installation and that's it. The script will tell you the correct command to run itself.

== Robust Way ==
Create the `run_sage` bash script:

{{{
#! /bin/bash
export SAGE_ROOT=/home/ondra/ext/sage
export SAGE_LOCAL=$SAGE_ROOT/local
export DOT_SAGE=~/.sage/
export PATH=$SAGE_ROOT/local/bin:$PATH
export LD_LIBRARY_PATH="$SAGE_ROOT/local/lib/openmpi:$SAGE_ROOT/local/lib/:"
export PYTHONPATH="$SAGE_ROOT/local/bin:$SAGE_ROOT/local/lib/python2.5/site-packages/setuptools-0.6c8-py2.5.egg:$SAGE_ROOT/local/lib/python2.5/site-packages/SQLAlchemy-0.4.3-py2.5.egg:$SAGE_ROOT/local/bin:$SAGE_ROOT/local/lib/python:$SAGE_ROOT/local/lib/python25.zip:$SAGE_ROOT/local/lib/python2.5/plat-linux2:$SAGE_ROOT/local/lib/python2.5/lib-tk:$SAGE_ROOT/local/lib/python2.5/lib-dynload:$SAGE_ROOT/local/lib/python2.5/site-packages:$SAGE_ROOT/local/lib/python2.5/site-packages/IPython/Extensions"
ipython
}}}
Then:

{{{
$ ./run_sage
Python 2.5.1 (r251:54863, Mar 29 2008, 09:29:46)
Type "copyright", "credits" or "license" for more information.
IPython 0.8.1 -- An enhanced Interactive Python.
? -> Introduction to IPython's features.
%magic -> Information about IPython's 'magic' % functions.
help -> Python's own help system.
object? -> Details about 'object'. ?object also works, ?? prints more.
In [1]: from sage.all import *
Falling back to a hard coded sage server in misc/hg.py
In [2]: var("x")
Out[2]: x
In [3]: x**2/4 + log(x)
Out[3]: log(x) + x^2/4
}}}