Create a virtualenv with Tornado

Virtualenv

# Install virtualenv
sudo pip install virtualenv

# Create the virtual envorinment
virtualenv --no-site-package app (# to use python3.5: `-p python3.5`)

# Install tornado in the virtual environment
app/bin/pip tornado

# After that, the following command should show something like tornado-VERSION-.egg
ls app/lib/python2.7/site-packages/

# Activeate virtual environment
source app/bin/activate
# your bash should look modified from this
#seba@dradisWork [14:52:53]
# to this
#(app) seba@dradisWork [14:52:53]

# Run the script using in-virtualenv python
bin/python2.7 webserver.py

=> web-server running

# Deactivate virtual environment
deactivate
# now the modified bash changes to its old self

Ref: http://www.programering.com/a/MDN1gDMwATg.html