Operations > Computing > FAQ

Python Module Installs

Local python module installs are possible using virtualenv, which should be installed on all the Linux Lab systems. In a terminal, run something like the following shell commands.

$ cd
$ mkdir python-stuff
$ cd python-stuff
$ virtualenv .
$ ./bin/pip install pandas
$ ./bin/pip install PyOpenGL

the last of which may take some time to compile. Consult the pip docs for more information on searching for and installing packages.

This custom install tree can then be used as follows:

$ echo 'print "Hello World"' > foo
$ cat foo
print "Hello World"
$ ./bin/python foo
Hello World

Or by editing the "shebang" line to reference the appropriate virtualenv path so that the script foo can be run directly:

$ pwd

Manually edit the file foo with your favorite editor to include the /homes/urlogin/python-stuff/bin/python line, as shown by the cat command:

$ cat foo
print "Hello World"
$ chmod +x foo
$ ./foo
Hello World

The virtualenv python should be the same version as the system one:

$ which python
$ python --version
Python 2.6.6
$ ./bin/python --version
Python 2.6.6

Environment variables such as PATH could be updated, and the env(1) command used to automatically select some virtualenv environment, but that will not be covered here.

Install Custom Python Version

If you need a specific version of python (e.g. 2.7 or 3.something), that custom version can be installed under your home directory as well; one way would be to manually build Python:

$ wget http://www.python.org/ftp/python/2.7.5/Python-2.7.5.tar.bz2
$ tar xjf Python-2.7.5.tar.bz2
$ cd Python-2.7.5
$ unset CFLAGS
$ ./configure --prefix=$HOME/usr/python-2.7.5 && make && make install

The CFLAGS environment variable likely does not need to be unset, but if you've enabled warnings and the like in CFLAGS like I had, the compile could core dump, good fun, good fun. Anyways! Scripts may then use the /homes/urlogin/usr/python-2.7.5/bin/python path to reference that custom python install, or virtualenv be used as above only this time using the custom python install:

$ cd
$ mkdir more-python-stuff
$ cd more-python-stuff
$ virtualenv --python=$HOME/usr/python-2.7.5/bin/python2.7 .
$ ./bin/python --version
Python 2.7.5

And then the same pip install and other instructions, above, should apply, only this time using the custom Python install under your home directory.

Manual Path Method

An alternative that may be less complicated than virtualenv though requires the creation of the filesystem paths and so forth is the manual path method:

$ mkdir -p ~/pyfoo/lib/python2.6/site-packages
$ export PYTHONPATH=~/pyfoo/lib/python2.6/site-packages
$ easy_install --prefix=~/pyfoo PyOpenGL
Using the tcsh shell, the setenv command must be used instead of export:
} mkdir -p ~/pyfoo/lib/python2.6/site-packages
} setenv PYTHONPATH /home/$USER/pyfoo/lib/python2.6/site-packages
} easy_install --prefix=~/pyfoo PyOpenGL
In either shell, the PYTHONPATH environment variable setting will likely need to be made permanent by editing a suitable shell configuration file, such as .bashrc or .cshrc, as a new shell will not otherwise set the custom value by default. Use the echo command to test whether the environment variable has been set:

Some Extant Modules

There may be python modules pre-installed under the following directory. However, these may not be maintained; more up-to-date versions more readily could be installed via the virtualenv method outlined above.

$ export PYTHONPATH=/home/lab.apps/pyfoo/lib/python2.6/site-packages

Cleanup Test Directories

Beware! Getting the rm command wrong might cause unexpected file deletion.

$ cd
$ rm -rf python-stuff more-python-stuff
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