QGIS functionality read off/edited in a Python script

How to write Python script in QGIS?

There are two options for writing Processing algorithms using Python. Within QGIS, you can use Create new script in the Scripts menu at the top of the Processing Toolbox to open the Processing Script Editor where you can write your code.
 

How do I run a Python file in QGIS?

The QGIS Python Console is an interactive shell for the python command executions. It also has a python file editor that allows you to edit and save your python scripts. Both console and editor are based on PyQScintilla2 package. To open the console go to Plugins ‣ Python Console ( Ctrl+Alt+P ).