Virtualenv way that you can separate different python enviroment for different porjects
eg. different package versions for different projects
pip install virtualenv
pip install pyOpenSSL ndg-httpsclient pyasn1 
You may need runtime/development packages for python and openssl as well in order for the build to succeed, e.g. python-dev libssl-dev libffi-dev on Ubuntu 14.04.
pip install --upgrade pip
pip list
#To export all package and version numbers for other projects
pip freeze  --local >> requirements.txt
# in new enviroment import/install package version
pip install -r requirements.txt
deactivate  # to getout of VE
# specify specific version of python to use
virtualenv -p /usr/bin/python2.7 py27_env
source py27_env/bin/activate
pip install -r requirements.txt
#virtualenvwrapper  allows to switch between different virtualenv
# Setup:
pip install virtualenvwrapper
path to virtualenvwrapper.sh  is mostly /usr/local/bin/virtualenvwrapper.sh
#  1. Create a directory to hold the virtual environments.
#     (mkdir $HOME/.virtualenvs).
#  2. Add a line like "export WORKON_HOME=$HOME/.virtualenvs"
#     to your .bashrc.
#  3. Add a line like "source /path/to/this/file/virtualenvwrapper.sh"
#     to your .bashrc.
#  4. Run: source ~/.bashrc
#  5. Run: workon
#  6. A list of environments, empty, is printed.
#  7. Run: mkvirtualenv temp
#  8. Run: workon
#  9. This time, the "temp" environment is included.
# 10. Run: workon temp
# 11. The virtual environment is activated.
#Create virtualenviroment
mkvirtualenv enviro100
mkvirtualenv enviro200
user1@localhost ~ $ workon
enviro100
enviro200
#To use enviroment named enviro200
workon enviro200