What is Flask?
Flask is a microframework for Python based on Werkzeug, Jinja 2 and good intentions.
What is Cloud9?
The online documentation of Cloud9 is very rich and helpful. The following help section explains how to get started with the online IDE.
How to install Flask on Cloud9?
The Cloud9 IDE provides developers with a bash terminal, which can be used to install Python packages. To install the Flask package the easy_install python module should be used:
sudo easy_install Flask
Hello World Flask Application
Create an app.py file within your Python application and enter the following code snippet:
Press F5 or click on the Run button to start your Flask application.
Your code is running at https://your-workspace-and-username-goeshere.c9.io.
Important: use os.getenv(PORT, 8080) as the port and os.getenv(IP, 0.0.0.0) as the host in your scripts!
Running on http://0.0.0.0:8080/
Now you could access your Flask application on the provided url.