You can download Python from this official link. Based on your OS (Windows or Linux or OSX), you might want to install Python 3 following these instructions.

It is always a great idea to sandbox your Python installation; and keeping it separate from your System Python. The System Python is the path to Python interpreter, which is used by other modules installed along with your OS.

It's not safe to install Python Web-frameworks or libraries directly using System Python. Instead, you can use Virtualenv to create and spawn a separate Python process when you are developing Python applications.

The Virtualenvwrapper module makes it easy for you to manage and sandbox multiple Python sandboxed environments in one machine; without corrupting any modules or services written in Python and used by your machine.

Of course, most cloud hosted development environment such as Nitrous or Cloud9 also comes with these pre-installed and ready for you to get coding! You can quickly pick a box from your dashboard, and start coding after activating a Python 3 environment.

In Cloud9, you need to select the Django box while creating a new development environment.

A few shell command examples would follow. If you wish to copy-paste, do note that the $ sign is a shorthand for the terminal prompt, it's not part of the command. My terminal prompt looks something like this:

alayek:~/workspace (master) $

And, an ls would look like

alayek:~/workspace (master) $ ls

But, while writing the same in this documentation, I would be writing it as

$ ls

Getting back to our discussion, you can create a Python 3 interpreter-included sandbox on Cloud9 by running on your cloud terminal:

$ mkvirtualenv py3 --python=/usr/bin/python3

You have to run it only once after creating a new box for your project. Once executed, this command would create a new sandboxed virtualenv ready for you to use, named py3.

To view available virtual environments, you can use

$ workon

To activate py3, you can use the workon command with the name of the environment:

$ workon py3

All three terminal commands above would also work on local Linux machines or OSX machines. These are virtualenvwrapper commands; so if you are planning on using them, make sure you have this module installed and added to PATH variable.

If you are inside a virtual environment; you can easily find that out by checking your terminal prompt. The environment name would be clearly shown in your terminal prompt.

For instance, when I am inside the py3 environment; I would be seeing this as my terminal prompt:

(py3)alayek:~/workspace (master) $

Notice the (py3) in braces! If for some reason, you are not seeing this, even if you are inside a virtual env; you can try doing one of the things mentioned here.

To get out of a virtual environment; or to deactivate one - use the command

$ deactivate

Again, this works only with virtualenvwrapper module.