View source for Python on the CS Linux Clients

All of the CS Department's [[:Category:Linux Clients|Linux clients]] have both Python 3 and Python 2.7 installed.  The default version is Python 3.  This page has some information about how Python works in our environment.

You may also want to read about [[Python on the CS Webservers]].

== Note: Python 2 is Deprecated ==

Although Python 2.7 is installed on our systems, it should only be used when needed for compatibility with older programs.  Official support for Python 2 ended in January 2020.  New programs should use Python 3, and old Python 2 programs may not work properly.  If a program does not work with Python 2, the solution is to [https://docs.python.org/3/howto/pyporting.html port it to Python 3].

Python 3 has been the default version of Python on our systems since early 2020.  We expect to completely remove Python 2 from our Linux clients once even the legacy packaging is no longer officially supported by our Linux distributor.

== Installing Python Packages ==

We try to have a good selection of the most-commonly-useful Python packages preinstalled on the Linux clients.  It sometimes happens that people need one or more packages that aren't currently installed.  Here's how you can get the packages you need.

=== pip ===

<code>pip</code> is installed on our systems, so if you need a package (and if it's in the Python Package Index), you can install it for your own personal use with:

 pip install --user ''package''

If you need a Python 2 package, use <code>pip2</code> instead of <code>pip</code>.

Note that, for ugrad accounts, the package will count against your [[Disk Quotas|disk quota]].

Removing a package you installed is as simple as:

 pip uninstall ''package''

<code>pip</code> will figure out on its own that it was locally-installed.

=== virtualenv ===

For complete control over what Python packages are available, you can use [https://virtualenv.pypa.io/en/stable/ virtualenv].  It uses a directory to hold a complete set of packages that are entirely independent from whatever is installed in the system (or in your home directory via <code>pip install --user</code>).

To use a virtual environment, pick a directory where it will keep its data and use the <code>virtualenv</code> program to initialize the directory.  For example, if you want to make a "project-1" environment and keep all of your environments in a "~/python" directory, you could do this:

 virtualenv ~/python/project-1

To start using the virtual environment, you must use one of the "activate" scripts in the environment's "<code>bin</code>" directory.  If your login shell is bash or zsh, use <code>activate</code> .  If you're using csh or tcsh, use <code>activate.csh</code> .  (See [[Shells Available for CS Accounts (bash, tcsh, etc.)#How to Tell What Shell You.27re Using|How to Tell What Shell You're Using]] if you're not sure what your shell is.)  Load the appropriate script with the <code>source</code> command:

 source ~/python/project-1/bin/activate

Your shell prompt will change to show the environment you're using.  No packages will be available to start with, but you can install them with "<code>pip install ''package''</code>" (without the "<code>--user</code>" parameter).

To leave the virtual environment, simply use the <code>deactivate</code> command:

 deactivate

If you have a ugrad account, you will need to make sure you don't exceed your [[Disk Quotas|disk quota]].

=== Request Systemwide Installation ===

If the package is likely to be useful for a number of different people or if there's some reason you can't install it into your home directory, you can ask us to install it systemwide via our [[Requesting Software Installation On A CS Linux or Windows Computer|software installation request procedure]].

Please note that, while we try to accommodate most requests, we cannot guarantee installation of any particular package.

[[Category:Linux Clients]]
[[Category:Software Available On The CS Linux Clients]]