[Cython] Optimising dict manipulation in extension types

[Stefan Behnel]

Hi,

tav wrote:
> Stefan Behnel wrote:
>> Who needs setters when you can modify "this" directly?
>>
>>        >>> def test():
>>        ...     a = []
>>        ...     def get(i):
>>        ...             return a[i]
>>        ...     return get
>>        >>> get = test()
>>        >>> get.func_closure[0].cell_contents.append(123)
>>        >>> get(0)
>>        123
> 
> Hehe =)
> 
> This bit of code protects against that: http://paste.lisp.org/display/70003

Nice. Having PJE in there makes me suspect that it might actually work.


>> Use a "cdef class" in Cython instead. It's implemented in C, so you need to
>> modify the class instance memory at the C level in order to change the object
>> in other ways than you allow. That's not secure, untrusted code may do that,
>> but it's not trivial and therefore pretty unlikely at least.
> 
> Untrusted code is pure Python only =)

ctypes?


> On a separate note, I am having trouble with dynamically returning a
> method (function) via __getattribute__. I'd like to be able to
> dynamically return attributes like __str__/__len__ -- and for them to
> be used by the likes of str(), len(), etc.

My guess is that this is because __str__ and friends are exposed at the C
level as part of the type struct. This likely overrides the __getattribute__
lookup mechanism.

Maybe you can just implement them and let them delegate to the right functions
instead.

Stefan