Solution to https://redd.it/7ifbd5 in Python

#RANDOM "MUSIC" GENERATOR
#Thanks to http://www.cyber-omelette.com/2017/01/markov.html for help with markov implementation.

import random

#so i can keep note info in one place
class note:
    def __init__(self, pitch='0', start='0', length='0'):
        self.pitch = pitch
        self.start = start
        self.length = length

def readdata():
    with open("data.txt") as rawdata:
        #converts the data into something more usable.
        #the data becomes a nested list. each item in the first list represents a note.
        #each item in the second list represents (in order) the pitch, start, and length of the note.
        data = str(rawdata.read()).split('\n')
        for i in range(len(data)):
            data[i] = data[i].split(' ')
        return data

def makepitchrule(data):
    #for now I'll only look one note back for reference
    #the pitch and length will be calculated seperately. Start can be ignored.
    #create reference for pitch of notes
    location = 1
    pitchrule = {}
    for pitch in data[location:]:
        key = data[location - 1][0]
        if key in pitchrule:
            pitchrule[key].append(pitch[0])
        else:
            pitchrule[key] = [pitch[0]]
        location += 1
    return pitchrule

def makelengthrule(data):
    #do the exact same thing, but with length
    #there's probably an easy way to combine these that I'm overlooking
    location = 1
    lengthrule = {}
    for length in data[location:]:
        key = data[location - 1][2]
        if key in lengthrule:
            lengthrule[key].append(length[2])
        else:
            lengthrule[key] = [length[2]]
        location += 1
    return lengthrule

def newnote(oldnote, pitchrule, lengthrule):
    #create a new note given the old note and the markov rules
    newnote = note()
    newnote.start = str(float(oldnote.start) + float(oldnote.length))
    newnote.pitch = random.choice(pitchrule[oldnote.pitch])
    newnote.length = random.choice(lengthrule[oldnote.length])
    return newnote

def writenote(currentnote, file):
    notestring = str(currentnote.pitch)+' '+str(currentnote.start)+' '+str(currentnote.length)+'\n' #just converting everything to strings "just in case"
    file.write(notestring)

#main program thing
data = readdata()
pitchrule = makepitchrule(data)
lengthrule = makelengthrule(data)
currentnote = note(random.choice(list(pitchrule.keys())), 0, random.choice(list(lengthrule.keys()))) #random first note
with open('music.txt', mode='wt') as file: #was gonna open in the writing funtion but that's a bad idea
    for i in range(100):
        writenote(currentnote, file)
        currentnote = newnote(currentnote, pitchrule, lengthrule)