AttributeError: 'str' object has no attribute 'write', youtube-dl kivy

I am working on a similar project and got the same error.

I catched Exceptions and print the traceback

import traceback

... 

  try:
     with youtube_dl.YoutubeDL(self.ydl_opts) as ydl:
        ydl.download([self.url])
  except Exception as inst:
     print(inst)
     tb = traceback.format_exc()
     print(tb)
     pass

and I got this :

'str' object has no attribute 'write'
Traceback (most recent call last):
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 797, in extract_info
    ie_result = ie.extract(url)
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/extractor/common.py", line 530, in extract
    ie_result = self._real_extract(url)
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/extractor/generic.py", line 2277, in _real_extract
    % (url, url), expected=True)
youtube_dl.utils.ExtractorError: 'qsd' is not a valid URL. Set --default-search "ytsearch" (or run  youtube-dl "ytsearch:qsd" ) to search YouTube

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "src/main.py", line 81, in run
    download_retcode = ydl.download([self.url])
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 2019, in download
    url, force_generic_extractor=self.params.get('force_generic_extractor', False))
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 820, in extract_info
    self.report_error(compat_str(e), e.format_traceback())
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 625, in report_error
    self.trouble(error_message, tb)
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 578, in trouble
    self.to_stderr(message)
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 527, in to_stderr
    self._write_string(output, self._err_file)
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 506, in _write_string
    write_string(s, out=out, encoding=self.params.get('encoding'))
  File "/home/odrevet/.local/lib/python3.6/site-packages/youtube_dl/utils.py", line 3180, in write_string
    out.buffer.write(byt)
AttributeError: 'str' object has no attribute 'write'

By looking to the function's name in the stack, we can see that our error occure when ytdl try to report another error (in this case : "youtube_dl.utils.ExtractorError: 'qsd' is not a valid URL", because I entered 'qsd' in my program instead of a valid url).

By looking in YoutubeDl.py in the function to_stderr we can see that out is supposed to be sys.stderr, and in utils.py in the function where the error occure :

def write_string(s, out=None, encoding=None):
    print(type(out))    # I added this line
    if out is None:
        out = sys.stderr
    assert type(s) == compat_str

    if sys.platform == 'win32' and encoding is None and hasattr(out, 'fileno'):
        if _windows_write_string(s, out):
            return

    if ('b' in getattr(out, 'mode', '')
            or sys.version_info[0] < 3):  # Python 2 lies about mode of sys.stderr
        byt = s.encode(encoding or preferredencoding(), 'ignore')
        out.write(byt)
    elif hasattr(out, 'buffer'):
        enc = encoding or getattr(out, 'encoding', None) or preferredencoding()
        byt = s.encode(enc, 'ignore')
        out.buffer.write(byt)    # Error on line 3180
    else:
        out.write(s)
  out.flush()

stderr has a buffer attribute according to the hasattr elif check, the problem is how Kivy is handling the error stream. According to the print I added in write_string, stderr is redefined as a <class 'kivy.logger.LogFile'> which do have a buffer attribute like the Stream it's supposed to be, but this attribute is a simple String.

See https://kivy.org/doc/stable/_modules/kivy/logger.html

class LogFile(object):

    def __init__(self, channel, func):
        self.buffer = ''     # <-- a str
        self.func = func
        self.channel = channel
        self.errors = ''

I don't known if it's possible to parameter kivy to use standard streams for stderr but I will check. Meanwhile catch the exception and print backtrace to at least have the original error before the "During handling of the above exception, another exception occurred"

edit: you can redirect stderr to a file

sys.stderr = open('./stderr', 'w')

I had the same problem when running my kivy app using youtube_dl on Android to download the audio track of a single video. The download of the same video audio worked ok on Windows 10.

I fixed the problem by changing the audio format in the youtube_dl options. Here's the code excerpt:

if os.name == 'posix':
    # on AndroidAndroid, FFmpegExtractAudio not available !
    self.ydlOutTmplFormat = '/%(title)s.mp3'

    self.ydl_opts = {
        #'format': 'bestaudio/best', # for unknown reason, not working on
                                     # Android when used by AudioDownloaderGUI !
        'format': 'worstaudio/worst',# This fixes the error "AttributeError:
                                     # 'str' object has no attribute 'write'"
        'quiet': YOUTUBE_DL_QUIET
    }
else:
    self.ydlOutTmplFormat = '\\%(title)s.%(ext)s'
    
    self.ydl_opts = {
        'format': 'bestaudio/best',
        'postprocessors': [{
            'key': 'FFmpegExtractAudio',
            'preferredcodec': 'mp3',
            'preferredquality': '128',
        }],
        'quiet': YOUTUBE_DL_QUIET
    }

I do not have any explanation why this modification solves the problem. When using youtube_dl on Android in a demo program not using kivy, the problem does not happen. Here's my demo code:

import os, re
import youtube_dl

if os.name == 'posix':
    targetAudioDir = '/storage/emulated/0/Download/Audiobooks/test_youtube_dl'
    ydl_opts = {
        'outtmpl': targetAudioDir + '/%(title)s.mp3',
        'format': 'bestaudio/best',
        #'format': 'worstaudio/worst',
        'quiet': False
    }
else:
    targetAudioDir = 'D:\\Users\\Jean-Pierre\\Downloads\\Audiobooks\\test_youtube_dl'
    ydl_opts = {
        'outtmpl': targetAudioDir + '\\%(title)s.%(ext)s',
        #'format': 'bestaudio/best',
        'format': 'worstaudio/worst',
        'postprocessors': [{
                            'key': 'FFmpegExtractAudio',
                            'preferredcodec': 'mp3',
                            'preferredquality': '96',
                        }],
    'quiet': False
    }

singlevideoUrl = 'https://youtu.be/Eqy6M6qLWGw'

with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    # downloading single video
    meta = ydl.extract_info(singlevideoUrl, download=False)
    videoTitle = meta['title']
    ydl.download([singlevideoUrl]) # not playable by kivy SoundLoader
    print('{} audio track downloaded'.format(videoTitle))

I had the same problem, and I solved it using the os library.

• First I create a convert.py script for example with the YouTube.dl function.

• Second, in kivy instead of calling YouTube.dl, I save the link in a .txt file, then I call os.system (python3 convert.py) using the txt with the link to convert and ready.