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import re
from fractions import Fraction
REGEX_NOTE = re.compile("([a-gA-GRr])([b#]*)([0-9]*)([.]*)([',]*)")
class NotationError(Exception):
pass
def parse_accidental(acc):
n = len(acc) if acc else 0
return -n if "b" in acc else n
def parse_octave(string):
"""5 is central octave. Return 5 as a fall-back"""
if string:
size = string.count(string[0])
return size + 4 if string[0] == "'" else -size + 5
else:
return 5
def parse_dur(dur, dots=""):
if dur == 0 or dur == "breve" or dur == "brevis":
base = 2
elif dur == "longa":
base = 4
elif dur == "maxima":
base = 8
else:
base = int(dur) ** -1
return sum([base / (2 ** x) for x in range(0, len(dots) + 1)])
def parse_note(note, volume=120, prev_octave=5, prev_dur=0.25):
note_names = "c # d # e f # g # a # b".split()
m = REGEX_NOTE.match(note)
if m:
pitch, acc, dur, dots, octv = m.groups()
else:
raise NotationError("You need to enter at least one note.")
octave = parse_octave(octv) if octv else prev_octave
duration = parse_dur(dur, dots) if dur else prev_dur
if pitch in ["r", "R"]:
return None, octave, duration, None
else:
pitch_number = note_names.index(pitch.lower())
acc_number = parse_accidental(acc)
note_number = (pitch_number + acc_number) % 12
return note_number, octave, duration, volume
def parse_notes(notes, volume=120):
# (number, octave, dur, volume)
prev_oct = 5 # default octave
prev_dur = 0.25 # default duration is 1/4, but it's 1 in the MIDI library
result = []
for item in notes:
number, octave, dur, vol = parse_note(item, volume, prev_oct, prev_dur)
result.append((number, octave, dur, vol))
prev_oct = octave
prev_dur = dur
return result
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