[Python-ideas] make __closure__ writable
andrew.svetlov at gmail.com
Sat Mar 17 02:44:01 CET 2012
I'm ok with mutable __closure__ but can you point the real use case?
On Fri, Mar 16, 2012 at 1:58 PM, Yury Selivanov <yselivanov.ml at gmail.com> wrote:
> Yes, your approach will work if your decorator is the only one applied.
> But, as I said, if you have many of them (see below), you can't just
> return a new function out of your decorator, you need to change the
> underlying "in-place". Consider the following:
> def modifier(func):
> orig_func = func
> while func.__wrapped__:
> func = func.__wrapped__
> # patch func.__code__ and func.__closure__
> return orig_func # no need to wrap anything
> def some_decorator(func):
> def wrapper(*args, **kwargs):
> # some code
> return func(*args, **kwargs)
> functools.wraps(wrapper, func)
> return wrapper
> def foo():
> # this code needs to be verified/augmented/etc
> So, in the above snippet, if you don't want to discard the
> @some_decorator by returning a new function object, you need to modify
> the 'foo' from the @modifier.
> In a complex framework, where you can't guarantee that your magic
> decorator will always be called first, rewriting the __closure__
> attribute is the only way.
> Again, since the __code__ attribute is modifiable, and __closure__
> works in tight conjunction with it, I see no point in protecting it.
> On 2012-03-16, at 3:24 PM, Mark Shannon wrote:
>> Yury Selivanov wrote:
>>> On 2012-03-16, at 2:57 PM, Yury Selivanov wrote:
>>>> Decorators can be nested, and what you can do in this case is to
>>>> find the most inner-wrapped function by traversing the '__wrapped__'
>>>> attributes (and check that the function you found is the actual
>>>> original function). After that you can play with its attributes,
>>>> but you can't simply substitute the function object, as the inner
>>>> decorator won't use it. So sometimes you have to work with the
>>>> function object without a way of substituting it.
>>> And that applies to the situations where decorators are not enough
>>> and you have to work on the opcode level.
>> Which you can do with a decorator.
>> Would this do what you want?
>> def f_with_new_closure(f, closure):
>> return types.FunctionType(f.__code__,
>> Python-ideas mailing list
>> Python-ideas at python.org
> Python-ideas mailing list
> Python-ideas at python.org
More information about the Python-ideas