Generates touch tones like on a telephone

dtmf.py

#!/usr/bin/env python3
# DTMF = Dual Tone Multi-Frequency
import itertools, math, pyaudio, random, sys
BITRATE = 8000
TONE_DURATION = 0.1 # seconds
KEY_FREQUENCIES = {
    '1': (697, 1209),
    '2': (697, 1336),
    '3': (697, 1477),
    'A': (697, 1633),
    '4': (770, 1209),
    '5': (770, 1336),
    '6': (770, 1477),
    'B': (770, 1633),
    '7': (852, 1209),
    '8': (852, 1336),
    '9': (852, 1477),
    'C': (852, 1633),
    '*': (941, 1209),
    '0': (941, 1336),
    '#': (941, 1477),
    'D': (941, 1633)
}

def sine_wave(frequency, frame=0):
    # Yield frames forever.
    while True:
        yield int(math.sin(frequency * frame * 2.0 * math.pi / BITRATE) * 63.0 + 128.0)
        frame += 1
def mix(*waves):
    # Add the waves.
    wave_iterators = [iter(wave) for wave in waves]
    while True:
        yield max(0, min(255, sum(next(wave) - 128 for wave in wave_iterators) + 128))
def mix_sine_waves(*frequencies):
    # Return the sum of sine waves at these frequencies.
    return mix(*[sine_wave(frequency) for frequency in frequencies])
def key_tone(key):
    # Return the wave that would play when this key is pressed.
    return mix_sine_waves(*KEY_FREQUENCIES[key])
def num_frames(seconds):
    # Return the number of frames in this number of seconds.
    return int(seconds * BITRATE)
def tone_for_duration(tone_generator, seconds):
    return bytes(itertools.islice(tone_generator, num_frames(seconds)))
def silence(seconds):
    return bytes(128 for i in range(num_frames(seconds)))

if __name__ == "__main__":
    random.seed()
    # Set up the audio output.
    p = pyaudio.PyAudio()
    try:
        stream = p.open(
            format=pyaudio.paUInt8,
            channels=1,
            rate=BITRATE,
            output=True
        )
        # Loop until the user enters a blank line.
        try:
            print("Enter a blank line to quit.")
            while True:
                user_input = input("Type a sequence of keys on a telephone keypad: ").strip().upper()
                if user_input:
                    # First, make sure that all the characters have tones defined.
                    valid = True
                    for c in user_input:
                        if c not in KEY_FREQUENCIES:
                            print(" > Error:", repr(c), "is not on the telephone keypad.")
                            valid = False
                    if valid:
                        # Play the dial tone.
                        sys.stdout.write(" > Off-hook...")
                        sys.stdout.flush()
                        stream.write(tone_for_duration(mix_sine_waves(350, 440), 1.5))
                        # Dial the numbers.
                        sys.stdout.write(" dialing ")
                        sys.stdout.flush()
                        stream.write(silence(0.1))
                        for c in user_input:
                            sys.stdout.write(c)
                            sys.stdout.flush()
                            # Write the dual-tone to the stream.
                            stream.write(tone_for_duration(key_tone(c), TONE_DURATION))
                            # Write a little bit of silence.
                            stream.write(silence(0.05))
                        # Write some additional silence.
                        sys.stdout.write("...")
                        sys.stdout.flush()
                        stream.write(silence(2.0))
                        # Play the ringback tone or busy signal.
                        if random.random() < 0.9:
                            sys.stdout.write(" ringing...")
                            sys.stdout.flush()
                            for i in range(4):
                                stream.write(tone_for_duration(mix_sine_waves(440, 480), 2.0))
                                stream.write(silence(4.0))
                        else:
                            sys.stdout.write(" busy signal...")
                            sys.stdout.flush()
                            for i in range(4):
                                stream.write(tone_for_duration(mix_sine_waves(480, 620), 0.5))
                                stream.write(silence(0.5))
                        print(" sequence complete.")
                else:
                    break
        finally:
            # Clean up.
            stream.stop_stream()
            stream.close()
    finally:
        p.terminate()