pytube.exceptions.RegexMatchError: get_throttling_function_name: could not find match for multiple

I used to download songs the following way:

from pytube import YouTube
video = YouTube('https://www.youtube.com/watch?v=AWXvSBHB210')
video.streams.get_by_itag(251).download()

Since today there is this error:

Traceback (most recent call last):
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\__main__.py", line 170, in fmt_streams
    extract.apply_signature(stream_manifest, self.vid_info, self.js)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\extract.py", line 409, in apply_signature
    cipher = Cipher(js=js)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\cipher.py", line 43, in __init__
    self.throttling_plan = get_throttling_plan(js)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\cipher.py", line 387, in get_throttling_plan
    raw_code = get_throttling_function_code(js)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\cipher.py", line 293, in get_throttling_function_code
    name = re.escape(get_throttling_function_name(js))
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\cipher.py", line 278, in get_throttling_function_name
    raise RegexMatchError(
pytube.exceptions.RegexMatchError: get_throttling_function_name: could not find match for multiple

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Me\Documents\YouTubeDownloader.py", line 3, in <module>
    video.streams.get_by_itag(251).download()
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\__main__.py", line 285, in streams
    return StreamQuery(self.fmt_streams)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\__main__.py", line 177, in fmt_streams
    extract.apply_signature(stream_manifest, self.vid_info, self.js)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\extract.py", line 409, in apply_signature
    cipher = Cipher(js=js)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\cipher.py", line 43, in __init__
    self.throttling_plan = get_throttling_plan(js)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\cipher.py", line 387, in get_throttling_plan
    raw_code = get_throttling_function_code(js)
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\cipher.py", line 293, in get_throttling_function_code
    name = re.escape(get_throttling_function_name(js))
  File "C:\Users\Me\AppData\Local\Programs\Python\Python39\lib\site-packages\pytube\cipher.py", line 278, in get_throttling_function_name
    raise RegexMatchError(
pytube.exceptions.RegexMatchError: get_throttling_function_name: could not find match for multiple

I had same issue when i was using pytube 11.0.0

so found out that there is a regular expression filter mismatch in pytube library in cipher.py class

function_patterns = [

    r'a\.C&&\(b=a\.get\("n"\)\)&&\(b=([^(]+)\(b\),a\.set\("n",b\)\)}};',
]

Now there is a update of pytube code yesterday to 11.0.1

function_patterns = [

    r'a\.[A-Z]&&\(b=a\.get\("n"\)\)&&\(b=([^(]+)\(b\)',
]

With this code update now downloading youtube video with pytube works!!!

Update your pytube library with this command:

python3 -m pip install --upgrade pytube