Launching an app in heroku? What is procfile? 'web:' command?

Question

I was referring to this site as i am learning python/flask and trying to use heroku.

http://ryaneshea.com/lightweight-python-apps-with-flask-twitter-bootstrap-and-heroku

Let me explain what all I did, so that any one who is stuck like me can get the picture. I am using Linux Backtrack command line . 1. I started virtualenv and then installed flask virtualenv --distribute pip install flask

Then, connected heroku and github, created a repo also in the github. Wrote a simple script and saved it in app.py

Then, asked to create a procfile! web: python app.py

Questions. 1. What is procfile in layman terms? 2. When i type web: python app.py, it says 'web:: command not found'

Please elaborate how this works?

I have one more doubt, sudo is supreme user right? We are not supposed to use it in virtualenv? And for what exactly are we using virtualenv? A simple example.

Questions are pretty basic. DO bare.

Answer 1

the Procfile tells Heroku what commands should be run (https://devcenter.heroku.com/articles/procfile).

You are able to define difference process types, such as web (the only one which will autostart by default), workers, etc...

So basically a Procfile containing

web: python app.py

is telling Heroku to started a named process called web, and to run python app.py when it starts.

There is Python specific documentation for Heroku at https://devcenter.heroku.com/articles/getting-started-with-python#declare-process-types-with-procfile