The of ( : ) what does it do?

[Frankduc]

Another question bothering me for a while:

In geeks example:

# code for testing decorator chaining
def decor1(func):
	def inner():
		x = func()
		return x * x
	return inner

def decor(func):
	def inner():
		x = func()
		return 2 * x
	return inner

@decor1
@decor
def num():
	return 10

print(num())

How do you know def decor(func): will be executed first to get to 400? I cant figure out the sequence of events. I tried with https://pythontutor.com/render.html#mode=display
I just dont get it.

But you are right it is a good writup.