You can download the VirtualBox image here:
If you need VirtualBox (a free download):
User is rpi and password is password.
The Ubuntu host that the VirtualBox image provides has Python & Geany installed on it so you can follow the programming tutorials at:
If you wish to emulate an actual ARM device, launch LXTerminal and:
which will download and unpack the Debian ARM disk image, a kernel and a launch file.
Enter the password for sudo (remembering that the password is password) and it will show a couple of lines of setup.
Launch xtightvncviewer from right at the bottom of the Other menu (click bottom left to get to the menus).
Type localhost and press return.
This will connect you to the Debian ARM 'screen' so you can actually see something.
Login as root, password is password.
cat /proc/cpuinfo and lo, you are in a copy of Debian that is running on an ARM processor.
Nothing is installed expect the bare minimum to get you in - it does have apt sources setup so you can start installing straightaway.
If you want to really confuse yourself, why not setup just like the Ubuntu host is:
apt-get install lxde xorg python geany
Ensure you click in the VNC viewer window so that when you are asked for keyboard/character set options you see the dialog boxes come up. If you forget, just click and press an up or down key to get the window to refresh.
As LXDE isn't keen on the root user logging in, add a new user:
You will be prompted to enter a new password - it is important that you remember it!
shutdown -r now
and when it comes back, you can login with your new user and password. You can surf the internet with IceWeasel (a bug fixed version of FireFox) and program Python with Geany.