[Python-ideas] make closure writable

Tue Mar 20 15:59:21 CET 2012

On 2012年03月20日, at 10:56 AM, Yury Selivanov wrote:
> Because usually you write decorators as functions, not classes. And
> when you do the former style, you usually do it in the following way:
>> def decorator(func):
> def wrapper(*args, **kwargs):
> return func(*args, **kwargs)
>> functools.wraps(wrapper, func)
> return wrapper
>> Now, let's use it:
>> @decorator
> def some_func(): pass
>> OK. At this point, 'some_func' object has a '__wrapped__' attribute,
> that points to original 'some_func' function. But whatever you write
> to 'some_func.__wrapped__' won't change anything, as the 'wrapper'
> will continue to call old 'some_func'. Instead of assigning something
> to __wrapped__, we need to change it in-place, by doing 
> '__wrapped__.__closure__ = new_closure'.

And as I told you in the first example: there is no problem when you have
only one decorator. You can surely just return a new FunctionType().
But when you have many of them, such as:
@decorator3
@your_magic_decorator_that_modifies_the_closure
@decorator2
@decorator1
def some_func(): pass
The only way to modify the __closure__ it to write to the __wrapped__ 
attribute of 'decorator1' wrapper.
-
Yury

[Python-ideas] make __closure__ writable

[Python-ideas] make closure writable