On Oct 31, 2008, at 6:00 AM, Stephane DROUARD wrote:
> Hello,
>
> In the documentation it is written that Cython defaults to the
> built-in scope when it can't determine the scope of a variable,
> which is different from Python, which defaults to the module scope.
The documentation needs to be fixed then. If the scope of a variable
can't be determined, then it actually raises a compile-time error.
> As a consequence, Cython needs module variables to be declared
> global to behave like under Python, resulting in a compatibility
> issue.
Could you give an example?
> Would it be possible to implement a compatibility mode, where
> Cython would behave as much as possible like Python?
This is certainly possible, but would have a significant performance
hit.
>
> Concerning undetermined variables, this could:
> - not cache them,
> - use a version of __Pyx_GetName() like below:
>
> static PyObject *__Pyx_GetName(PyObject *dict, PyObject *name) {
> PyObject *result;
> result = PyObject_GetAttr(dict, name);
> // If not found and the dictionary is the module, try in builtin.
> if (!result && dict == __pyx_m) {
> PyErr_Clear();
> result = PyObject_GetAttr(__pyx_b, name);
> }
> if (!result)
> PyErr_SetObject(PyExc_NameError, name);
> return result;
> }
>
>
> An improvement could be:
> - declare them (static PyObject *__pyx_builtin_xxx = NULL) but do
> not initialize them through __Pyx_InitCachedBuiltins(),
> - access them through a function that first checks if the variable
> is initialised (!= NULL), so return it, otherwise do something like
> above,
> - if the attribute is got from builtin, update the pointer.
Again, this is a performance hit, and wouldn't handle the case that a
module-level variable with the name of a module global is assigned at
some later point in the program.
> During the tests, I remarked that:
>
> import __builtin__
> print __builtin__.__name__
>
> __name__ is not cached. A possible improvement ;-)
But what if I did
import __builtin__
print __builtin__.__name__
foo()
print __builtin__.__name__
where foo (defined elsewhere) is
def foo():
import __builtin__
__builtin__.__name__ = "something else"
Thanks for your comments.
- Robert
_______________________________________________
Cython-dev mailing list
[email protected]
http://codespeak.net/mailman/listinfo/cython-dev
