The_Official_Raspberry_Pi_-_Beginner’s_Book_Vol1,_2018 (1)

160 THE OFFICIAL RASPBERRY PI BEGINNER'S GUIDE

Greetings from Python

Load Thonny, in either simple or standard modes, by clicking on the Raspbian menu icon,

choosing Programming, and clicking on either Thonny link. If you’re using the Sense HAT

emulator and it gets covered by the Thonny window, click and hold the mouse button on either

window’s title bar – at the top, in blue – and drag it to move it around the desktop until you can

see both windows.

To use the Sense HAT, or Sense HAT emulator, in a Python program, you need to import the

Sense HAT library. Type the following into the script area, remembering to use sense_emu (in

place of sense_hat) if you’re using the Sense HAT emulator:

from sense_hat import SenseHat

sense = SenseHat()

The Sense HAT library has a simple function for taking a message, formatting it so that it

can be shown on the LED display, and scrolling it smoothly. Type the following:

sense.show_message("Hello, World!")

Save your program as Hello Sense HAT, then click the Run button. You’ll see your message

scroll slowly across the Sense HAT’s LED matrix, lighting up the LED pixels to form each letter

in turn (Figure 7-7). Congratulations: your program’s a success!

PYTHON LINE CHANGE

Python code written for a physical Sense HAT runs on the Sense

HAT emulator, and vice-versa, with only one change. If you’re using

the Sense HAT emulator with Python you’ll need to change the line

from sense_hat import SenseHat in all the programs from

this chapter to from sense_emu import SenseHat instead.

If you want to then run them on a physical Sense HAT again, just

change the line back!