Python Decortors - Small question

Question

we have the code
.....................................................
def decor(func):
def wrap():
print("============")
func()
print("============")
return wrap

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

decorated = decor(print_text)
decorated()
..............................................................
that's cool and I understand that completely, but why did i put another function (wrap) i think it's just a waste of time, couldn't I type this code...
...........................................................
def decor(func):
print("============")
func()
print("============")

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

decor(print_text)
..................................................................
basically, i called the function 'print_text' inside the function 'decor', isn't that easier??

Answer 1

Karim Maasarani ,

here is a link to some comments about your question:

> https://stackoverflow.com/questions/45335580/why-do-we-need-wrapper-function-in-decorators#45336189

Answer 2

Notice how you are calling function in both versions.

In first version, you are calling the function by:
-> decorated()

in the second:-
-> decor(print_text)

Try to modify the second function call to look like first:
-> decorated = decor(print_text)
-> decorated()
_____________________________________

Above leads to error because, in the second version you are not returning callable from "decor()". (see sololearners explanation)

If we don't use "wrap" inner function, we have to modify "decorated()" to "decor(print_text)" and this might not be easy if the function we are modifying is used many times in our project and could lead to errors. Using an inner function saves us from all this extra work.

Answer 3

your second example is not a decorator. It's just a function calling another function. Notice you are using the decorator function name.

In a decorator pattern, you use the inner function name. The decorator modifies the result.
Also, passing arguments in your second example becomes tricky.

Answer 4

#you need a wrapper function inside.
#try to make the same generic decorator without the inner wrap function.

#generic decorator
def allcaps(foo):
def wrap(*a,**kw):
return foo(*a,**kw).upper()
return wrap

#normal functions
def hello(n):
return f"hello {n}"

def goodbye(n):
return f"bye {n}"

#normal results
print(hello('peter'))
print(goodbye('megan'))

#decorated functions
@allcaps
def hello(n):
return f"hello {n}"

@allcaps
def goodbye(n):
return f"bye {n}"

#decorated results
print(hello('peter'))
print(goodbye('megan'))

Answer 5

Thank you @Lothar @sandeep @Mirielle @Bob_Li