python lines that start with @

Question

Possible Duplicate:
Understanding Python decorators

I was reading a django app source code where I find this

@login_required
def activities(request = None,\
            project_id = 0,\
            task_id = 0,\
            ...

What does the line that start with @ mean?

http://stackoverflow.com/questions/739654/understanding-python-decorators — , Jul 15 '11 at 18:46
+1 because it is a valid question, because you don't know, that you have to search for decorators when you see the `@` symbol the first time. — Framester, Apr 23 '15 at 13:57
Also the right duplicate would be http://stackoverflow.com/questions/6392739/what-does-the-at-symbol-do-in-python — Framester, Apr 23 '15 at 13:59

score 5 · Answer 1 · answered Jul 15 '11 at 18:47

It's a decorator. What it does is basically wrap the function. It is equivalent with this code:

def activities(request = None,\
            project_id = 0,\
            task_id = 0,\
            ...
activities = login_required(activities)

It is used for checking function arguments (in this case request.session), modifying arguments (it may give the function other arguments than it passes), and maybe some other stuff.

score 4 · Answer 2 · answered Jul 15 '11 at 18:46

It's a decorator, which is a special type of function (or class, in some cases) in Python that modifies another function's behavior. See this article.

@decorator
def my_func():
    pass

is really just a special syntax for

def my_func():
    pass
my_func = decorator(my_func)

score 3 · Accepted Answer · edited May 23 '17 at 12:18

3

Please check out Python Decorators Explained. It has an amazing answer that will explain everything.

edited May 23 '17 at 12:18

Community

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answered Jul 15 '11 at 18:46

TorelTwiddler

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score 0 · Answer 4 · answered Jul 15 '11 at 18:47

0

It is a decorator. It's a syntatic sugar for:

def activities(request = None,\
            project_id = 0,\
            task_id = 0,\
            ...

activities = login_required(activities)

answered Jul 15 '11 at 18:47

utdemir

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python lines that start with @

4 Answers4