Python sys.prefix

Balazs Zachar zachar at awst.at
Fri Jan 22 09:39:50 CET 2010


It looks like the python install environment is easily movable between 
two machine with the same OS (I mean, with the correct libraries)...
Can I use this in production?

Please consider the following test, after I use ./configure 
--prefix=/opt/python2.6.4 && make && make install:

[root at CentOS-5-4-test1 ~]# /opt/python2.6.4/bin/python
Python 2.6.4 (r264:75706, Jan 20 2010, 20:26:15)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-46)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
...import sys
...sys.prefix
'/opt/python2.6.4'
...sys.path
['', '/opt/python2.6.4/lib/python26.zip', 
'/opt/python2.6.4/lib/python2.6', 
'/opt/python2.6.4/lib/python2.6/plat-linux2', 
'/opt/python2.6.4/lib/python2.6/lib-tk', 
'/opt/python2.6.4/lib/python2.6/lib-old', 
'/opt/python2.6.4/lib/python2.6/lib-dynload', 
'/opt/python2.6.4/lib/python2.6/site-packages']


[root at CentOS-5-4-test1 ~]# mv /opt/python2.6.4/ /opt/python2.6.4_newplace
[root at CentOS-5-4-test1 ~]# /opt/python2.6.4_newplace/bin/python
Python 2.6.4 (r264:75706, Jan 20 2010, 20:26:15)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-46)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
...import sys
...sys.prefix
'/opt/python2.6.4_newplace'
...sys.path
['', '/opt/python2.6.4_newplace/lib/python26.zip', 
'/opt/python2.6.4_newplace/lib/python2.6', 
'/opt/python2.6.4_newplace/lib/python2.6/plat-linux2', 
'/opt/python2.6.4_newplace/lib/python2.6/lib-tk', 
'/opt/python2.6.4_newplace/lib/python2.6/lib-old', 
'/opt/python2.6.4_newplace/lib/python2.6/lib-dynload', 
'/opt/python2.6.4_newplace/lib/python2.6/site-packages']


On 01/21/2010 05:56 PM, zachar at awst.at wrote:
> Hi All,
>
> I need some help about my "problem":
> I compiled and installed python with ./configure --prefix=/opt/pyhon2.6.4... But I have to move it to a different directory (the reason is very difficult but I must do this)... I started the interpreter from shell and I was surprised because It still worked and It changed the sys.prefix so it pointed to the correct place so the sys.path was correct.... The questions are: HOW? Is it a feature which is not documented (at least I couldn't find anything about it)?
>
>  From the official python documentation (http://docs.python.org/library/sys.html?highlight=sys#sys.prefix):
> "sys.prefix¶
>
>      A string giving the site-specific directory prefix where the platform independent Python files are installed; by default, this is the string '/usr/local'. This can be set at build time with the --prefix argument to the configure script. The main collection of Python library modules is installed in the directory prefix + '/lib/pythonversion' while the platform independent header files (all except pyconfig.h) are stored in prefix + '/include/pythonversion', where version is equal to version[:3]."
>
> In my case, this is not correct: it looks, after I call the interpreter, something change the sys.prefix variable and point it to the right place and not to that directory which I used with the configuration script... This is very useful (I am happy because it solves one of my problems) but I am afraid of it will be do it in a different way in the future (as it is not documented).
>
> Thanks,
> Regards,
> Balazs
>    




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