How to make Python file run by double-clicking on it in Ubuntu 20.04?

I make a game in Python with the turtle module but I want to make it executable by double clicking on it. I follow these steps:

1. My Python file has #!/usr/bin/env python3 on top.

2. I created a file called launcher.desktop on the desktop. It contains:

   [Desktop Entry]
   Name = Pong 
   Exec = /home/username/Desktop/MyGame/game.py 
   Version = 1.0 
   Icon = /home/username/Desktop/MyGame/game.icon 
   Type = Application
   

3. I marked the file as executable.

However, when I double-click on that file, it opens in text editor.

Can someone tell me how can I make the Python file executable by double-clicking in Ubuntu 20.04?

Your desktop file is basically correct, double clicking it will be interpreted as "edit" - you can see it in the properties - the default behavior of an icon on a desktop will be "Text editor".

I'd put it into ~/.local/share/applications. Then you could start it from the activities. Make sure the exec expression is executable. So your "game.py" must either be executable (then it needs the shebang #!/usr/bin/env python3 in its first line) or the exec must look like:

Exec= /usr/bin/python3 /path/to/mygames/game.py

Note that it would be good style to have the follwing line as first line in your desktop file:

#!/usr/bin/env xdg-open

And the "icon" should be rather *.png than ".icon".

So I called the game "pong":

[]

from where you could put it to your "favorites"

This is the complete desktop file as shown above:

#!/usr/bin/env xdg-open
[Desktop Entry]
Encoding=UTF-8
Name = Pong 
#Exec = /usr/bin/python3 /home/username/Desktop/games/game.py 
Exec = /home/username/Desktop/games/game.py 
Version = 1.0 
Icon = /home/username/Desktop/games/game.png
Type = Application
NoDisplay=false
Categories=Games