pygame-play-tone.py

# Generate a 440 Hz square waveform in Pygame by building an array of samples and play
# it for 5 seconds.  Change the hard-coded 440 to another value to generate a different
# pitch.
#
# Run with the following command:
#   python pygame-play-tone.py

from array import array
from time import sleep

import pygame
from pygame.mixer import Sound, get_init, pre_init

class Note(Sound):

    def __init__(self, frequency, volume=.1):
        self.frequency = frequency
        Sound.__init__(self, self.build_samples())
        self.set_volume(volume)

    def build_samples(self):
        period = int(round(get_init()[0] / self.frequency))
        samples = array("h", [0] * period)
        amplitude = 2 ** (abs(get_init()[1]) - 1) - 1
        for time in xrange(period):
            if time < period / 2:
                samples[time] = amplitude
            else:
                samples[time] = -amplitude
        return samples

if __name__ == "__main__":
    pre_init(44100, -16, 1, 1024)
    pygame.init()
    Note(440).play(-1)
    sleep(5)

I believe there is a typo in line 25, saying xrange instead of range. After fixing it, the tone played. How do I send the correction as a pull request/revision?

@TrumpetDude That is not a typo. In Python 2 we have both range and xrange. The difference is that range returns an enumeration whereas xrange returns an iterator.

In Python 3 xrange was renamed to range replacing the original range method.

There are many subtle changes like this between Python 2 and 3 that you might like to be aware of, see the What's New In Python 3.0 article for more examples :)