Utshaw's questions

My OS: Ubuntu 20.04LTS
python --version: Command python not found
python3 --version: Python 3.8.2

Kazam was working well. I regularly upgrade packages using sudo apt-get update; sudo apt-get upgrade commands. I also update OS using update-manager -c command. So, one day kazam has stopped working. It gives the following error:

/usr/bin/kazam:32: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
  from gi.repository import Gtk
WARNING Kazam - Failed to correctly detect operating system.
Traceback (most recent call last):
  File "/usr/bin/kazam", line 147, in <module>
    from kazam.app import KazamApp
  File "/usr/lib/python3/dist-packages/kazam/app.py", line 36, in <module>
    from kazam.backend.prefs import *
  File "/usr/lib/python3/dist-packages/kazam/backend/prefs.py", line 30, in <module>
    from kazam.backend.webcam import Webcam
  File "/usr/lib/python3/dist-packages/kazam/backend/webcam.py", line 24, in <module>
    from gi.repository import GObject, GUdev
  File "/usr/lib/python3/dist-packages/gi/importer.py", line 132, in load_module
    raise ImportError('cannot import name %s, '
ImportError: cannot import name GUdev, introspection typelib not found

I had run sudo ln -s /usr/bin/python3 /usr/bin/python for a different purpose. After some days the following happened: (Don't know how the system installed this python version)
python --version: Python 2.7.18rc1
Later I deleted the symbolic link too. So, now python command outputs Command not found.

When I tried to install Cisco packet tracer from deb file it gave the following error:

Unpacking packettracer (7.3.0) ...
dpkg: dependency problems prevent configuration of packettracer:
 packettracer depends on libdouble-conversion1; however:
  Package libdouble-conversion1 is not installed.
 packettracer depends on qt-at-spi; however:
  Package qt-at-spi is not installed.

dpkg: error processing package packettracer (--install):
 dependency problems - leaving unconfigured
Processing triggers for gnome-menus (3.32.0-1ubuntu1) ...
Processing triggers for desktop-file-utils (0.24-1ubuntu1) ...
Processing triggers for mime-support (3.63ubuntu1) ...
Processing triggers for shared-mime-info (1.10-1) ...
Errors were encountered while processing:
 packettracer

Then I tried installing libdouble-conversion1 using command sudo apt-get install libdouble-conversion1 . It gives the following error

Package libdouble-conversion1 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'libdouble-conversion1' has no installation candidate

Every time I change volume I hear "beep" noise. How can I remove this ?

There is no way to remove "Alert Sound" in the settings. I am forced to select any of the 4 choices. I'm not sure whether alert sound has anything to do with my problem. Accepted answer of This question couldn't solve this issue.

I can't change any settings inside Screen Lock portion as they are grayed out. Settings options for other categories seems okay.
How can I fix this ?

How can I install Blender 2.78a ? The file extension is .tar.bz2 . I have found this but as 10.04 is much older and I am installing a different file I felt that I need to learn specific instruction for installing blender .

I almost know nothing about coding in Ubuntu. I am currently dual booting ubuntu 16.04 LTS and Windows 10. Everything was fine . But today an error occured saying

"can't find filesystem"

and then grub rescue begins . After searching for some time I have found out solution that tells to do these:

ls
set prefix=(hd0,msdos5)/boot/grub
insmod normal
normal

I know that ls is listing harddrive partitions(let me know if I am wrong) .Then(in set prefix) I need to select a partition . There came a error when I selected msdos5. After some try I selected msdos6. Then it ran . But the problem is that from another solution to this problem I wrote this code:

set boot=(hd0,msdos6)

I think I messed up . Probably , it involves which partition of the harddisks is going to boot .Now, my laptop is running after writing this code and every time I turn on the laptop the boot stuck at the beginning showing the same error & I need to write the code every time I need to run the laptop . How can I solve this issue? I probably also need to know the partition which is booting (msdos*) & I don't know how to find that.