Most of the time you read about setting up virtual environments, it is for web development. But the same benefits hold for analysis and research software. You want to be able to reproduce results. It also increases security not to be adding all the unverified libraries with machine level privileges. This post is a minor modification of the outstanding-tutorial I have been using for the last few months. Since it is two years old, there is another version of python and it does not cover IPython, I will repeat the steps here.
First install Pythonbrew and another version of python
I use apt-get in ubuntu so type
cd ~ sudo apt-get install libsqlite3-dev libbz2-dev libxml2-dev libxslt-dev curl
Then get pythonbrew:
``curl -kL http://github.com/utahta/pythonbrew/raw/master/pythonbrew-install | bash``
This line gets the repository and executes through bash. We will need to modify the configuration file for bash.
echo "source $HOME/.pythonbrew/etc/bashrc" >> ~/.bashrc
Don’t forget the dot in
.bashrc. Now nothing changes until this file is executed by the operating system:
This should complete with no errors. The next step is to install python 2.7.3. It is going to take a few minutes to complete.
pythonbrew install --verbose 2.7.3
And now we have to tell the system to use this new version of python
pythonbrew use 2.7.3
Install virtualenv and virtualenvwrapper
We have to install virtualenv in the system’s python and virtualenvwrapper in the new python.
sudo apt-get install python-virtualenv pip install virtualenvwrapper
The first line only needs to be executed once. It works for the whole system. The second one needs to be done for each new python environment you create. Make a hidden directory to hold the virtual environments.
Add the following three lines at the end of your .bashrc.
export WORKON_HOME=$HOME/.virtualenvs`` export VIRTUALENVWRAPPER_PYTHON=$HOME/.pythonbrew/pythons/Python-2.7.3/bin/python`` source $HOME/.pythonbrew/pythons/Python-2.7.3/bin/virtualenvwrapper.sh``
You will need to use an editor. Then you have to reload them:
Create the virtual environment
To create a virtual environment called ‘no-more-drug-war’, type:
mkvirtualenv --no-site-packages no-more-drug-war
So, in order to know what packages we have installed at any time, we install yolk.
pip install yolk
Do not type sudo! To see what it installed at any time:
A list of further packages for IPython are available here. Type these individually and they each may take a few minutes to install.
pip install pyzmq pip install pygments pip install tornado pip install nose pip install numpy pip install scipy pip install matplotlib pip install pandas
Turning it on and off
Now to get out of your virtual environment, just type
To get back in, type: