[Pyrex] cdef private class ... ?

[Stefan Behnel]

Hi,

I was thinking about module namespace pollution a bit more. What about adding
a class modifier "private" that keeps a class from appearing in the module
dictionary?

The reasoning is that it is not so uncommon to define a non-public class, e.g.
for passing internal (C) values through Python space or for keeping
"self-deallocating" context pointers around. Currently, there isn't a way to
say: "the module uses that class internally, but the user shouldn't care", and
especially "the user *must not* instantiate that class" for whatever reason
(uninitialised pointer fields, for example). The easiest way to deal with that
would be to just keep the class name out of the module dictionary.

I know that this is not a 'secure' solution as users can still instantiate it
when they get an instance in their hands, but I don't consider that worth
bothering. I'm more concerned about having it pop up when you say
"dir(module)". If users don't get in touch with it unless they explicitly
introspect it, that's by far enough.

Also, since we were discussing some optimisation ideas on the Cython list
lately, this would allow the compiler to see (or enforce?) that the class
'can' not be subclassed from Python space so that it can optimise away some
overhead like garbage collection support if the class doesn't contain Python
object fields, or the Python instantiation overhead if the class doesn't use
__init__() - instantiation could automatically use the tp_new() fast path in
that case.

I considered "static", which is the C equivalent, but since that has a totally
different meaning in another C-like big-buzzword coffee-language, I prefer
"private" here, which I find much more explicit.

Any comments?

Stefan