Linux
# CentOS
sudo yum -y update
sudo yum -y install centos-release-SCL # the package is part of CentOS Extras repository
sudo yum -y install python27
source /opt/rh/python27/enable
virtualenv my_venv
source my_venv/bin/activate# Ubuntu
sudo apt-get update
sudo apt-get install virtualenv
virtualenv my_venv
source my_venv/bin/activate
Mac OS X
easy_install virtualenv
virtualenv my_venv
source my_venv/bin/activateWindows
Download Python installer and install making sure you check the Add Python 3.5 to PATH checkbox. In cmd.exe run:
pip install virtualenv
virtualenv my_venv
my_venv\Scripts\activate