[Python-Dev] Python 2.3a1's mandatory use of cyclic GC causes existing applications to fail (original) (raw)

Christian Tismer tismer@tismer.com
Thu, 06 Feb 2003 20:46:33 +0100

Thomas Heller wrote:

[extending slots]

May I suggest to use an ordered sequence (of pairs) instead of a dict for slots. Then you also can completely control the layout that C code sees and construct C compatible structures or other data types from pure Python code.

Huh, are you fast! I was about to propose exactly this same thing: If we deal with flat types, then we also can define their precise layout.

Using a dict would anyway be nicer to read, because the colons are quite illustrative. For literal dicts, it would be imaginable to hook into the build_dict and grab the objects from the stack in order... ...I see Guido's head shaking :-)

Another way would be not to go away from slots as a simple list, but allow to use structure objects with the necessary attribute like name, type, whatever instead of the name strings. This could go as far as to also allow redefining getters and setters at the same time.

Is this going too far? Am I re-inventing something like CTypes?

At first thought, I'd stick with [(name, type), ...], just to get things started.

Here's how ctypes does it: It's named fields instead of slots, and typically you write something like this

class Point(Structure): fields = [("x", "i"), ("y", "i")] which defines a Python objects having x and y instance vars, which must be integers. ctypes extends this so that instead of the (struct module compatible) format specified "i", also Python objects are allowed which describe a C data type.

What would this C data type be? Other structs as well, or only atomic types? Do you think of even specifying (name, bitsize, alignment), or is this overdone?

ciao - chris

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