sound.length not returning correctly about python-for-android HOT 7 CLOSED

E/MediaPlayer(12471): Attempt to call getDuration without a valid mediaplayer
E/MediaPlayer(12471): error (-38, 0)

import os, csv
from glob import glob

from pydub import AudioSegment

from flatten import flatten

cur_dir = os.path.dirname(__file__)
media_dir = os.path.join(os.path.dirname(cur_dir), 'media')
sound_paths = (glob(os.path.join(x[0], '*.ogg')) for x in os.walk(media_dir))
# Flatten it, since the lists might contain other lists
south_paths_flattened = list(flatten(sound_paths))

with open('sound_lengths.csv', 'w') as csvfile:
    csvwriter = csv.writer(csvfile, delimiter=',', lineterminator='\n')

    for sound_path in south_paths_flattened:
        print("sound_path: %s" % sound_path)
        try:
            sound = AudioSegment.from_ogg(sound_path)
        except Exception:
            print("Could not load file.")
        else:
            csvwriter.writerow([os.path.normpath(sound_path),
                                str(len(sound) / 1000.)])

class FixedSoundLoader(object):
    """
    A custom factory class that substitutes for SoundLoader to avoid issue
    https://github.com/kivy/python-for-android/issues/67

    """
    sound_lengths = {}

    @staticmethod
    def load_sound_lengths():
        with open('sound_lengths.csv', 'r') as csvfile:
            csvreader = csv.reader(csvfile, delimiter=',')
            for row_number, row in enumerate(csvreader):
                print(repr(row))
                FixedSoundLoader.sound_lengths[row[0]] = float(row[1])

    @staticmethod
    def load(sound_file_path):
        sound_file_path = os.path.normpath(sound_file_path)

        if not FixedSoundLoader.sound_lengths:
            FixedSoundLoader.load_sound_lengths()

        sound = SoundLoader.load(sound_file_path)

        try:
            sound_length = FixedSoundLoader.sound_lengths[sound_file_path]
        except KeyError:
            # If we don't have this sound on record in the CSV, hope
            # that the length method actually words
            pass
        else:
            # It's actually the _get_length method we must overrride, as per
            # https://github.com/kivy/kivy/blob/master/
            #                          kivy/core/audio/__init__.py
            sound._get_length = lambda : sound_length

        return sound