function address4

def a(x, y):
    print("I am from function a")
    return x(y)
def b(z):
#    z()    run the function outside def b(z) on line 13
    print("I am from function b")
    def d():
        print("I am from inner function d")
    z() #run the function on line 13
    def c():       #register the address of function c with the content below. Function c is not run until function c is called outside on line 9.
        print("I am from function c")
    return c, d #return only 1 value out as a tuple (c, d)
def d():
    print("I am from function d")

a(b,d)[1]() #(c, d)[1]()
a(b,d)[0]() #(c, d)[0]()