gendral doubt about looping

Hi, i am architecture student, now a days i use grasshopper a lot. i have background in coding so arriving at algorithm is not a problem but i am limited in my knowledge. 

every time when i think of solution , almost all complex solution has looping in it. if its single level of looping then i can manage with hoop snake plugin. but when i have nested loop .its get complicated. i couldn't do entirely in scripting because its easy for me to do a function in grasshopper.

is there any option to define a grasshopper definition as function in python scripting ?

how generally people deal with nesting loops without scripting platform?