The pygame module is a set of highly portable modules that runs on most operating systems. We will use the mixer module from pygame to play the sound files.

Assuming that you have installed the package, let's begin by importing pygame (see code 3.06.py):

import pygame

According to the official API documentation of the mixer module at http://www.pygame.org/docs/ref/mixer.html, we need to initialize pygame before we can play back the audio files.

We initialize pygame in a new method called init_pygame (see code 3.06.py):

def init_pygame(self):
 pygame.mixer.pre_init(44100, -16, 1, 512)
 pygame.init()

The mixer.pre_init method is a special requirement for our drum machine because the lack of it causes a lot of sound lagging. We will not get into the details of audio programming here, but suffice to say that the arguments to the pre_init method are as follows:

pre_init(frequency=22050, size=-16, channels=2, buffersize=512) 

After pygame is initialized like this, the documentation suggests the following code to play the sound. Let's add this to our code as well (see code 3.06.py):

 def play_sound(self, sound_filename):
   if sound_filename is not None:
      pygame.mixer.Sound(sound_filename).play()