scale name >> key signature

scalifier.py

octave = ['C',('C#','Db'),'D',('D#','Eb'),'E','F',('F#','Gb'),'G',('G#','Ab'),'A',('A#','Bb'),'B']
 
def is_valid_scale_name(scalename):
  if len(scalename) > 2: return False
  if len(scalename) == 2 and scalename[1] != 'b': return False
  if scalename[0].upper() not in 'ABCDEFG': return False
  return True
 
def find_note(name):
  for i in range(len(octave)):
    note = octave[i]
    if isinstance(note,str):
      if note == name:
        return i
    elif((name == note[0]) or (name == note[1])):
      if name in note:
        return i
 
def get_note(index,is_flat_scale):
  note = octave[index]
  if isinstance(note,str):
    return note
  else:
    if is_flat_scale:
      return note[1]
    else:
      return note[0]
 
def is_flat_scale(tonenumber):
  if(tonenumber<6):
    return tonenumber%2==1
  else:
    return tonenumber%2==0
 
def name_to_key_sig(scalename):
  pos = find_note(scalename)
  if is_flat_scale(pos):
    return next_flat(pos, [])
  else:
    return next_sharp(pos,[])
 
def next_sharp(pos, signature):
  if pos == 0:
    return signature
  else:
    signature = next_sharp((pos-7)%12,signature)
    signature.append(get_note(pos-1,False))
    return signature

def next_flat(pos, signature):
  if pos == 0:
    return signature
  else:
    signature = next_flat((pos-5)%12, signature)
    signature.append(get_note((pos+5)%12, True))
    return signature

if __name__ == '__main__':
  try:
    while 1:
      scalename = raw_input('scale name: ')
      if is_valid_scale_name(scalename):
        print name_to_key_sig(scalename)
      else:
        print 'Enter a valid scale name. Ex: A, Bb, C'
  except KeyboardInterrupt:
    print
    import sys
    sys.exit(1)