#! /usr/bin/env python """ Create a simple stereo file containing a sine tone at 441 Hz, using onlypython's built-in modules. """ import waveimport mathimport struct  def create_sine_wave(freq, samplerate, nframes, nchannels):    """ create a pure tone (without numpy) """    _x = [0.7 * math.sin(2. * math.pi * freq * t / float(samplerate))          for t in range(nframes)]    _x = [int(a * 32767) for a in _x]    _x = b''.join([b''.join([struct.pack('h', v)                             for _ in range(nchannels)])                   for v in _x])    return _x  def create_test_sound(pathname, freq=441, duration=None,                      framerate=44100, nchannels=2):    """ create a sound file at pathname, overwriting exiting file """    sampwidth = 2    nframes = duration or framerate  # defaults to 1 second duration    fid = wave.open(pathname, 'w')    fid.setnchannels(nchannels)    fid.setsampwidth(sampwidth)    fid.setframerate(framerate)    fid.setnframes(nframes)    frames = create_sine_wave(freq, framerate, nframes, nchannels)    fid.writeframes(frames)    fid.close()    return 0  if __name__ == '__main__':    import sys    if len(sys.argv) < 2:        sys.exit(2)    sys.exit(create_test_sound(sys.argv[1]))