You will have to setup python (the version you want ) from the official website:

https://www.python.org

and use any text editor I suggest atom :

https://atom.io

Then type your code in it and after that save your file with this extension (filename.py) go to it's directory and open powershell or terminal there just type this in the terminal: python filename.py

You should type this:

Print (str (123))

As str () converts type only to a string one it is not supposed to print any output