What is the use of "wrap" function?

Question

Why does the following code come out with an "Nonetype"error?

def decor(func):
print("============")
func()
print("============")

def print_text():
print("Hello world!")

print_text = decor(print_text)

print_text();

Answer 1

print_text == None, because decor() returns None.
try:

def decor(f):
#....

@decor
def print_text():
#...

print_text()

or:

def decor(func):
def s():
print('....')
func()
print('....')
return s

def print_text():
#....

print_text=decor(print_text)
print_text()