Where did comment-line go from Emacs?

Question

emacs

Salute comrades!
I recently came across an interesting event: I open one python script, I want to comment out a line, I press the "default" Cx C-; and I get a message that this combination is not defined (???). Okay, I press Mx and type in comment-line , and it's gone (???)
What happened that I missed, everything was working a couple of months ago.
GNU Emacs 24.5.1

Answer 1

Select the desired line and press Alt-; (comment/uncomment). And it works for all languages.