extrakto.py invalid syntax

[yueyihui]

a@vdi:~/.tmux/plugins/extrakto$ ./extrakto.py
  File "./extrakto.py", line 49
    key = f"alt{i}"
                  ^
SyntaxError: invalid syntax

a@vdi:~/.tmux/plugins/extrakto$ bash --version
GNU bash, version 5.1.0(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

a@vdi:~/.tmux/plugins/extrakto$ python --version
Python 3.6.13

[laktak]

I am unable to reproduce this issue with Python 3.6.9.

extrakto.py uses

#!/usr/bin/env python3

so maybe your python3 symlink is incorrect - try python3 --version.