Understanding how does a decorator really work [duplicate]

This question already has an answer here:

How to make a chain of function decorators?

16 answers

I'm starting studying decorators and I already hit an obstacle. First here is my code.

 def deco (f):



    def coucou():

        print("this is function{}".format(f))

        return f()

    return coucou



@deco

def salut():

    print("salut")





def hi():

    return salut()

I will try to explain my problem as well as I can with my bad English. If I understand it this is how things should happen: I execute my hi() function which returns salut() and because salut is modified by the decorator coucou will be executed and coucou returns ....... salut(), what i mean is that I expect an infinite loop but that doesn't happen and I don't understand why. Can anyone explain practically how decorators work?

edited Jan 19 at 0:33

Ondrej K.

2,80361022

asked Jan 19 at 0:06

Newgate Ace

184

marked as duplicate by Bazingaa, Noctis Skytower, Community♦ Jan 19 at 1:08

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

realpython.com/primer-on-python-decorators This may help in understanding how decorators work

– Pro Q
Jan 19 at 0:20

You may also want to have a look at the documentation: PEP-318 and PEP-3129.

– Ondrej K.
Jan 19 at 0:29

add a comment |

This question already has an answer here:

How to make a chain of function decorators?

16 answers

I'm starting studying decorators and I already hit an obstacle. First here is my code.

 def deco (f):



    def coucou():

        print("this is function{}".format(f))

        return f()

    return coucou



@deco

def salut():

    print("salut")





def hi():

    return salut()

edited Jan 19 at 0:33

Ondrej K.

2,80361022

asked Jan 19 at 0:06

Newgate Ace

184

marked as duplicate by Bazingaa, Noctis Skytower, Community♦ Jan 19 at 1:08

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

realpython.com/primer-on-python-decorators This may help in understanding how decorators work

– Pro Q
Jan 19 at 0:20

You may also want to have a look at the documentation: PEP-318 and PEP-3129.

– Ondrej K.
Jan 19 at 0:29

add a comment |

This question already has an answer here:

How to make a chain of function decorators?

16 answers

I'm starting studying decorators and I already hit an obstacle. First here is my code.

 def deco (f):



    def coucou():

        print("this is function{}".format(f))

        return f()

    return coucou



@deco

def salut():

    print("salut")





def hi():

    return salut()

edited Jan 19 at 0:33

Ondrej K.

2,80361022

asked Jan 19 at 0:06

Newgate Ace

184

This question already has an answer here:

How to make a chain of function decorators?

16 answers

I'm starting studying decorators and I already hit an obstacle. First here is my code.

 def deco (f):



    def coucou():

        print("this is function{}".format(f))

        return f()

    return coucou



@deco

def salut():

    print("salut")





def hi():

    return salut()

This question already has an answer here:

How to make a chain of function decorators?

16 answers

python python-3.x decorator

edited Jan 19 at 0:33

Ondrej K.

2,80361022

asked Jan 19 at 0:06

Newgate Ace

184

edited Jan 19 at 0:33

Ondrej K.

2,80361022

asked Jan 19 at 0:06

Newgate Ace

184

edited Jan 19 at 0:33

Ondrej K.

2,80361022

edited Jan 19 at 0:33

Ondrej K.

2,80361022

edited Jan 19 at 0:33

Ondrej K.

2,80361022

asked Jan 19 at 0:06

Newgate Ace

184

asked Jan 19 at 0:06

Newgate Ace

184

asked Jan 19 at 0:06

Newgate Ace

184

marked as duplicate by Bazingaa, Noctis Skytower, Community♦ Jan 19 at 1:08

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

marked as duplicate by Bazingaa, Noctis Skytower, Community♦ Jan 19 at 1:08

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

realpython.com/primer-on-python-decorators This may help in understanding how decorators work

– Pro Q
Jan 19 at 0:20

You may also want to have a look at the documentation: PEP-318 and PEP-3129.

– Ondrej K.
Jan 19 at 0:29

add a comment |

realpython.com/primer-on-python-decorators This may help in understanding how decorators work

– Pro Q
Jan 19 at 0:20

You may also want to have a look at the documentation: PEP-318 and PEP-3129.

– Ondrej K.
Jan 19 at 0:29

realpython.com/primer-on-python-decorators This may help in understanding how decorators work

– Pro Q
Jan 19 at 0:20

You may also want to have a look at the documentation: PEP-318 and PEP-3129.

– Ondrej K.
Jan 19 at 0:29

add a comment |

1 Answer
1

active

oldest

votes

The f in coucou is the undecorated (original) version of salut.

answered Jan 19 at 0:10

Scott Hunter

33.3k74071

yeah but why and how? again if i got it, the decorator modify the function in its definition and makes it point permanently to the function returned by the decorator, am i wrong?

– Newgate Ace
Jan 19 at 0:13

1

@NewgateAce it doesn't modify the original function. It creates a new function, and returns a new function. So the global name salut now refers to the function returned by the decorator, i.e. coucou, but coucou's local name f, which is a free variable closed over by coucou, still refers to the original function

– juanpa.arrivillaga
Jan 19 at 0:16

@NewgateAce in other words, there is nothing magical about the decorator syntax. It is equivalent to def my_function(): ...; my_func = deco(my_func)

– juanpa.arrivillaga
Jan 19 at 0:24

@juanpa.arrivillaga i see now, f = deco(f) makes it clearer for me. thanks for your reply.

– Newgate Ace
Jan 19 at 0:30

@juanpa.arrivillaga what im about to say might be stupid, but when i print "salut" and "deco(salut)", they dont have the same reference ...

– Newgate Ace
Jan 19 at 0:46

|
show 1 more comment

1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

The f in coucou is the undecorated (original) version of salut.

answered Jan 19 at 0:10

Scott Hunter

33.3k74071

yeah but why and how? again if i got it, the decorator modify the function in its definition and makes it point permanently to the function returned by the decorator, am i wrong?

– Newgate Ace
Jan 19 at 0:13

1

@NewgateAce it doesn't modify the original function. It creates a new function, and returns a new function. So the global name salut now refers to the function returned by the decorator, i.e. coucou, but coucou's local name f, which is a free variable closed over by coucou, still refers to the original function

– juanpa.arrivillaga
Jan 19 at 0:16

@NewgateAce in other words, there is nothing magical about the decorator syntax. It is equivalent to def my_function(): ...; my_func = deco(my_func)

– juanpa.arrivillaga
Jan 19 at 0:24

@juanpa.arrivillaga i see now, f = deco(f) makes it clearer for me. thanks for your reply.

– Newgate Ace
Jan 19 at 0:30

@juanpa.arrivillaga what im about to say might be stupid, but when i print "salut" and "deco(salut)", they dont have the same reference ...

– Newgate Ace
Jan 19 at 0:46

|
show 1 more comment

The f in coucou is the undecorated (original) version of salut.

answered Jan 19 at 0:10

Scott Hunter

33.3k74071

yeah but why and how? again if i got it, the decorator modify the function in its definition and makes it point permanently to the function returned by the decorator, am i wrong?

– Newgate Ace
Jan 19 at 0:13

1

@NewgateAce it doesn't modify the original function. It creates a new function, and returns a new function. So the global name salut now refers to the function returned by the decorator, i.e. coucou, but coucou's local name f, which is a free variable closed over by coucou, still refers to the original function

– juanpa.arrivillaga
Jan 19 at 0:16

@NewgateAce in other words, there is nothing magical about the decorator syntax. It is equivalent to def my_function(): ...; my_func = deco(my_func)

– juanpa.arrivillaga
Jan 19 at 0:24

@juanpa.arrivillaga i see now, f = deco(f) makes it clearer for me. thanks for your reply.

– Newgate Ace
Jan 19 at 0:30

@juanpa.arrivillaga what im about to say might be stupid, but when i print "salut" and "deco(salut)", they dont have the same reference ...

– Newgate Ace
Jan 19 at 0:46

|
show 1 more comment

The f in coucou is the undecorated (original) version of salut.

answered Jan 19 at 0:10

Scott Hunter

33.3k74071

The f in coucou is the undecorated (original) version of salut.

answered Jan 19 at 0:10

Scott Hunter

33.3k74071

answered Jan 19 at 0:10

Scott Hunter

33.3k74071

answered Jan 19 at 0:10

Scott Hunter

33.3k74071

answered Jan 19 at 0:10

Scott Hunter

33.3k74071

yeah but why and how? again if i got it, the decorator modify the function in its definition and makes it point permanently to the function returned by the decorator, am i wrong?

– Newgate Ace
Jan 19 at 0:13

1

@NewgateAce it doesn't modify the original function. It creates a new function, and returns a new function. So the global name salut now refers to the function returned by the decorator, i.e. coucou, but coucou's local name f, which is a free variable closed over by coucou, still refers to the original function

– juanpa.arrivillaga
Jan 19 at 0:16

@NewgateAce in other words, there is nothing magical about the decorator syntax. It is equivalent to def my_function(): ...; my_func = deco(my_func)

– juanpa.arrivillaga
Jan 19 at 0:24

@juanpa.arrivillaga i see now, f = deco(f) makes it clearer for me. thanks for your reply.

– Newgate Ace
Jan 19 at 0:30

@juanpa.arrivillaga what im about to say might be stupid, but when i print "salut" and "deco(salut)", they dont have the same reference ...

– Newgate Ace
Jan 19 at 0:46

|
show 1 more comment

yeah but why and how? again if i got it, the decorator modify the function in its definition and makes it point permanently to the function returned by the decorator, am i wrong?

– Newgate Ace
Jan 19 at 0:13

1

@NewgateAce it doesn't modify the original function. It creates a new function, and returns a new function. So the global name salut now refers to the function returned by the decorator, i.e. coucou, but coucou's local name f, which is a free variable closed over by coucou, still refers to the original function

– juanpa.arrivillaga
Jan 19 at 0:16

@NewgateAce in other words, there is nothing magical about the decorator syntax. It is equivalent to def my_function(): ...; my_func = deco(my_func)

– juanpa.arrivillaga
Jan 19 at 0:24

@juanpa.arrivillaga i see now, f = deco(f) makes it clearer for me. thanks for your reply.

– Newgate Ace
Jan 19 at 0:30

@juanpa.arrivillaga what im about to say might be stupid, but when i print "salut" and "deco(salut)", they dont have the same reference ...

– Newgate Ace
Jan 19 at 0:46

yeah but why and how? again if i got it, the decorator modify the function in its definition and makes it point permanently to the function returned by the decorator, am i wrong?

– Newgate Ace
Jan 19 at 0:13

@NewgateAce it doesn't modify the original function. It creates a new function, and returns a new function. So the global name salut now refers to the function returned by the decorator, i.e. coucou, but coucou's local name f, which is a free variable closed over by coucou, still refers to the original function

– juanpa.arrivillaga
Jan 19 at 0:16

@NewgateAce in other words, there is nothing magical about the decorator syntax. It is equivalent to def my_function(): ...; my_func = deco(my_func)

– juanpa.arrivillaga
Jan 19 at 0:24

@juanpa.arrivillaga i see now, f = deco(f) makes it clearer for me. thanks for your reply.

– Newgate Ace
Jan 19 at 0:30

@juanpa.arrivillaga what im about to say might be stupid, but when i print "salut" and "deco(salut)", they dont have the same reference ...

– Newgate Ace
Jan 19 at 0:46

|
show 1 more comment

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