how to run python script without typing 'python ...'

You've got to add the shebang:

#!/usr/bin/env python

Then make the script executable:

chmod +x foo

Then you can run it like any other executable:

./foo

And a note from Homer6: if you're editing the file from windows and invoking it on linux, you may run into the cryptic "No such file or directory" error. It's due to the line endings of the lines being CRLF instead of LF. If you convert them to LF, the script will execute as expected. Notepad++ > View > Show Symbols > Show End of Line to show the EOL characters. And Notepad++ > Edit > EOL Conversion > Unix Format to convert all line endings to use LF. Alternatively, you can use the dos2unix tool (dos2unix foo.py), which is present on most Linux systems.

1. Add a line at the top of your script:

   #! /usr/bin/env python
   

2. Rename your script from script_name.py to script_name
3. make the script executable: chmod +x script_name

The line at the top selects the same python that you get when typing python at the prompt. You can also specify a direct path:

#!/opt/python/3.6/bin/python

It didn't really apply to your personal scripts but as you are quoting beets, note that it is also possible to automate this action when you are distributing your packages, thanks to setuptools entry_point option.
So if you are distributing a package like myModule and want to make the main_function() function accessible via typing mymodulescript in the console you would probably add something like this to your setup.py file :

setup(
    # your other arguments ..
    entry_points={
        'console_scripts': [
            'mymodulescript = myModule:main_function'
        ]
    }
)