To run a python script there are two approaches.

Suppose the script is called script.py.

You can always do this from the terminal:

$ python3 script.py


Alternatively, you can make the script executable.

This requires that the first line of the script give the path to python3:

#! /usr/bin/python3

If you don't know where python3 is you can find it like this:

$ which python3

Now we need to tell the OS that script.py is an executable file type.

To make a python script script.py executable:

$ chmod +x script.py

Now you can run the script like this:

$ ./script.py