Hardware Reference
In-Depth Information
As in previous adventures, you will use Python 3 to create the jukebox controls.
1.
Open IDLE 3 by double-clicking the desktop icon or by selecting the application
from the main menu. Click File
➜
New Window to open a new text ile.
Alternatively, you could use a command line text editor like nano.
2.
In the irst line, as in previous projects using Python, you import the modules
and libraries that you need. For example, the
glob
module is used for getting a
list of MP3 iles in a directory, the
random
module is used to shule the MP3
iles inside the list,
sys
is used for
sys.exit
and getting command line argu-
ments, and
vlc
is the Python interface to the
vlc
library
libvlc
. Type:
import glob, random, sys, vlc
3.
Leave a one-line gap underneath and then type:
if len(sys.argv) <= 1:
print(“Please specify a folder with mp3 files”)
sys.exit(1)
sys.argv
is a list that contains the arguments passed to the program on the
command line. You may remember in earlier adventures we accessed programs
from the command line. For instance, if you typed
sudo python3 jukebox.
py /home/pi/music
into the command line, then the list would contain
jukebox.py
at position 0 and
/home/pi/music
at position 1 (the zero posi-
tion always contains the name of the program that was run). So the irst argu-
ment is at position 1.
4.
he next part of the program will load a list of MP3s:
folder = sys.argv[1]
files = glob.glob(folder+”/*.mp3”)
if len(files) == 0:
print(“No mp3 files in directory”, folder, “..exiting”)
sys.exit(1)
As described before, position 1 in
sys.argv
is the irst command line argu-
ment. he
glob
function allows you to get a list of iles matching a pattern. he
pattern
“*.mp3”
expands to any ile which ends in
.mp3
, so
files = glob.
glob(folder+”/*.mp3”
) will produce a list of all iles ending in
.mp3
inside
the folder given on the command line. If the directory contains no MP3s there
won't be anything for the jukebox to play, so you exit early using
sys.exit
.
5.
Now you are able to use the
random
module to shule the list of MP3 iles to
put them in a random order. Underneath the previous code, type:
random.shuffle(files)
