Setting up virtualenv


LIGO Data Grid users on Scientic Linux 6 systems will need to perform a one-time setup of pip and virtualenv, as the versions installed on Scientic Linux 6 are too old for use with PyCBC. Note that once this part of the installation has been performed, you should not need to do it again.

You need at least version 7.1.0 of pip to manage the installation process for virtualenv. Run the command

pip --version

to determine the version of pip that you have installed. If you have version 7.1.0 or greater, you can continue to the section Install virtualenv without installing pip. If this command returns pip: command not found or a version of pip less than 7.1.0, then follow the instruction in the section to Install pip

Install pip

First install pip in your home directory. In this example, we install in the directory ${HOME}/local/. Run the commands

VERSION=`python -c 'import sys; print "%d.%d" % (sys.version_info[0], sys.version_info[1])'`
mkdir -p ${HOME}/local/pip-7.1.0/lib/python${VERSION}/site-packages
export PYTHONPATH=${HOME}/local/pip-7.1.0/lib/python${VERSION}/site-packages
export PATH=${HOME}/local/pip-7.1.0/bin:${PATH}

to set up your environment to install pip. Note that when setting PYTHONPATH we have excluded all other directories from the path. This is to prevent the install process from picking up any existing libraries that may be in your PYTHONPATH. When setting PATH, the pip install directory is placed at the start of the PATH so that it is found first by the shell.

Now use the system version of easy_install to install pip 7.1.0 in this directory with the command

easy_install --prefix=${HOME}/local/pip-7.1.0

Next check that you are using the correct version of pip by running the command

pip --version

This should report pip 7.1.0. If it returns an older version, check that you set your PATH and PYTHONPATH correctly.

Install virtualenv

Install virtual env using the version of pip that you just inst

pip install virtualenv --upgrade --user

This installs virtualenv into your ${HOME}/.local directory where pip installs user packages. (Note the period at the start of .local).


If this command returns Can not perform a '--user' install. User site-packages are not visible in this virtualenv. then you are already in a Python virtual environment. You will need to deactivate this environment or contact your system administrator to install virtualenv for you in this environment.

Add virtualenv to your path by running the command

export PATH=${HOME}/.local/bin:${PATH}

You may want to add this command to your .bash_profile so that virtualenv is available when you log in by running

echo 'export PATH=${HOME}/.local/bin:${PATH}' >> ${HOME}/.bash_profile

You can now continue installing PyCBC.