#!/usr/bin/python

A = 440
notes = {
    'C' :  0,
    'D' :  2,
    'E' :  4,
    'F' :  5,
    'G' :  7,
    'A' :  9,
    'B' :  11,
}

rel = (2**(1/12.))
def note2freq(name):
    sharp = name[1] == '#'
    flat  = name[1] == 'b'
    if sharp or flat:
        note = name[0:1]
        octave = int(name[2])
    else:
        note = name[0]
        octave = int(name[1])
    num = notes[note]
    if sharp:
        num += 1
    if flat:
        num -= 1
    fullnum = num + 12*(octave - 5)
    return A*rel**(fullnum + 3)

if __name__ == '__main__':
    test_fmt = '{:3} gave {: 9.2f} Hz\nexpected {: 9.2f} Hz'
    def test(name, expected):
        print(test_fmt.format(name, note2freq(name), expected))

    test('C2' ,  65.41)
    test('Ab4', 415.30)
    test('A4' , 440.00)
    test('B4' , 493.88)
    test('B#4', 523.25)
    test('Cb5', 493.88)
    test('C5' , 523.25)
    print()
    test('E4' , 329.63)
    test('B3' , 246.94)
    test('G3' , 196.00)
    test('D3' , 146.83)
    test('A2' , 110.00)
    test('E2' ,  82.41)