Please, could somebody explain this code step by step?

Question

Please, could somebody explain this code step by step?
This really seems impossible to understand to me.
Although I have no problem with function with 2 arguments, seems impossible understand function with 3 argunemts.

def add(x,y):
return (x+y)
>>>>> this code il clear and simple to understand, return first value added to second one.

def do_twice(func,x,y):
return func(func(x,y),func(x,y))
>>>>> this is arabic!
>>>>> func(x,y) works like add(x,y)? why?
>>>>> which is the real value of func? why if I remove it after "return" command , outputs are 15,15?
>>>>> which is the meaning of comma between first and secondo func(x,y)?

a=5
b=10
print (do_twice(add,a,b))

Please Help!

Answer 1

def add(x, y):
return x + y
#add(x,y) => add(a, b) => add(5,10)
#return 5 + 10 = 15

def do_twice(func, x, y):
return func(func(x, y), func(x, y))

#do_twice (func, x, y) =>
#do_twice (add, a, b) =>
#return add(add(a,b), add(a, b))=>
#return add(add(5,10), add(5,10))
#return add(15, 15)
#return 15 + 15 = 30

""" the print(do_twice(add, a, b)) changes func to add, x to a,and y to b.
At this point do_twice returns the first function add(x,y) twice, then finally solves a third add(x,y) by adding 15 + 15. """

a = 5
b = 10

print(do_twice(add, a, b))

Answer 2

:3