Virtualenv is a python tool for creating isolated python environments. 'Virtualenv' is extremely useful for testing/installing python packages without affecting the other system(python) packages. Its very useful if you have two applications hosted on the same server & each of them are using different versions of django, sentry,celery etc.


Here, in this article I will explain how to create virtualenv's & how we can use it effectively. Again, this narrates the installation & configuration of virtualenv on a Ubuntu box. For installing python libraries, we have 'two' alternate ways. One is to use 'easy_install' & other is 'pip'. I will be using 'pip'.


First, we need to have some packges installed on our Ubuntu box. This includes python-setuptools, python-dev, build-essential,python-pip etc. That can be achieved by running the below command,

sudo apt-get install python-setuptools python-pip python-dev build-essential

Now, you are Good to Go.

sudo pip install virtualenv

The above command will install virtualenv for you. If you are behind a proxy, you have to specify your proxy machine's IP & Port in the pip install command. It will look like the one below,

sudo pip install --proxy=proxy-ip:proxy-port virtualenv (Replace proxy-ip & proxy-port with appropriate values)

Eg: sudo pip install --proxy=192.168.1.5:3128 virtualenv

If you not behind a proxy, you can skip the above step.

Next, we need to create & activate the virtualenv. Prior to that, you must locate the place on your ubuntu box where you are going to create your custom virtualenv. Here, I will be creating the virtualenv under my 'Home Directory' say, /home/user.

cd /home/user

virtualenv --no-site-packages my-venv

Here, 'my-venv' is the name of the virtualenv that we created. '--no-site-packages' will tell virtualenv not to symlink the global site packages into my local environment.

Now, we need to activate the virtualenv.

source /home/user/my-venv/bin/activate

The above command will activate the 'my-venv' virtualenv. Now move inside the my-venv folder.

cd /home/user/my-venv

It will have some contents/folder like mentioned below,

bin  include  lib  local

cd bin ( Move to bin directory )

ls

The contents inside bin directory will look similar to the ones below,

activate      activate.fish     easy_install      pip      python
activate.csh  activate_this.py  easy_install-2.7  pip-2.7

Next, we can try installing django inside 'my-venv' virtualenv. At the moment we are inside /home/user/my-venv/bin directory, if not move inside that folder.

./pip install django

If you need a partcular version of django say, 1.3, it can be achieved as follows,

./pip install django==1.3

again, if you are behind a proxy,


sudo pip install --proxy=proxy-ip:proxy-port django==1.3 (Replace proxy-ip & proxy-port with appropriate values)

Eg: sudo pip install --proxy=192.168.1.5:3128 django==1.3


Similarly, you can create a number of virtualenv's to be used for separate applications.


Now, when your need is over, you can safely deactivate the virtualenv. Issue the below command on the terminal,

deactivate

Note: The above instructions will work on Ubuntu machines only.