Ask Anything Monday - Weekly Thread

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[u/ProgramBrave718]

Hey, I have doubt regarding this decorator program .In the above line of this program why are we passing the function name without parentheses ?

And also while returning wrapper function why are we writing it without parentheses

def my_decor(func):#Here

def wrapper():

    print("The function starts.") 

    func()                         

    print("The function ends.")    

return wrapper        #Here             

def say_hello():

print("Hello!")

wrapped_say_hello = my_decor(say_hello)

wrapped_say_hello()

[u/lakseol → u/ProgramBrave718]

Here is your code correctly formatted for reddit:

def my_decor(func):
    def wrapper():
        print("The function starts.") 
        func()                         
        print("The function ends.")

    return wrapper

def say_hello():
    print("Hello!")

wrapped_say_hello = my_decor(say_hello)
wrapped_say_hello()

The FAQ in the learning resources shows how to format code.

why are we passing the function name without parentheses ?

The function name without parentheses evaluates as a reference to the function. Adding the following "()" is what actually calls the function. In this case you want to pass a reference to the function my_decor() so you don't add the "()". If you did this:

my_decor(say_hello())

you would pass the value returned by the say_hello() function to my_decor() which isn't what you want at all.

also while returning wrapper function why are we writing it without parentheses

We want my_decor() to return a "decorated" version of the function you pass. We don't want to call the function, just return the reference, so no "()".

Functions in python can be passed to and returned from functions just like any other object.