I accidentally deleted python3.6 from my ubuntu-18.04, and now when I reboot my computer it requires username and password and gets me shell
Solution 1:
I have also encountered this problem recently， so here is my solutions.
The above error is because the connection is not available, so you can not use apt install command directly. The key point to connect to network can refer Configure WiFi Connections, maybe you should reboot your ubuntu after doing this.
Then you can run the command sudo apt-get install --reinstall ubuntu-desktop, it may take a few minutes.
Finally, I hope to help you guys who have also encountered the same problem.