The python module Flask is a small web framework.
Install the module using pip.
(my_new_env)[free-tutorials@free-tutorials ~]$ pip install Flask
Downloading/unpacking Flask
  Downloading Flask-0.9.tar.gz (481kB): 481kB downloaded
  Running setup.py egg_info for package Flask
    
    warning: no files found matching '*' under directory 'tests'
    ...
    ...
Successfully installed Flask Werkzeug Jinja2
Cleaning up... Create the next python script and save as : flask-web.py .
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
    return 'Hello World!'
if __name__ == '__main__':
    app.run() Run the python script:
(my_new_env)[free-tutorials@free-tutorials ~]$ python flask-web.py 
 * Running on http://127.0.0.1:5000/
127.0.0.1 - - [25/Jan/2013 00:10:35] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [25/Jan/2013 00:10:36] "GET /favicon.ico HTTP/1.1" 404 -
127.0.0.1 - - [25/Jan/2013 00:10:36] "GET /robots.txt HTTP/1.1" 404 -
127.0.0.1 - - [25/Jan/2013 00:10:36] "GET /favicon.ico HTTP/1.1" 404 -
127.0.0.1 - - [25/Jan/2013 00:10:36] "GET /robots.txt HTTP/1.1" 404 - You will see something like this:

Also you can try the quickstart tutorial here.