While this isnt impossible - its definetly not intended, when python runs PyType_Ready() it converts the PyGetSetDef's into PyObject's attribute descriptors which are stored in the PyType's dictionary. so strongly advice against trying to manipulate that data at low level... some alternatives could be....

• define pygetattro and manage the lookups on each call - typical way to handle such cases.
• you could look at assigning properties to a class as can be done in python...

MyClass.foo = property(getx, setx, delx, "This is a property")

... doing in C will be more verbose of course but it should work fine.

On Thu, Jul 5, 2012 at 1:42 PM, Mateusz Loskot <mateusz@loskot.net> wrote:

Hi,

I have a type object implemented using plain Python 3 C API. The type has number of attributes - tp_getset slot set with typical table of geters and seters. I'd like to find out best way to make certain attributes read-only at run-time.

The table I assign to tp_getset looks like this:

PyGetSetDef Foo_getseters[] = { {"text", (getter)Foo_get_text, (setter)Foo_set_text, PyDoc_STR("Foo text"), NULL }, {NULL} };

Now, at some point at run-time, I'd like to disallow assignment to .text property Obvious way to do that is to check desired condition in Foo_set_text() and set AttributeError.

I wonder if it would be possible and sensible to modify the tp_getset slot and simply set the Foo_set_text entry in Foo_getseters to NULL.

Is it possible? Is there any better way to make an attribute read-only at run-time?

Best regards,

Mateusz Loskot, http://mateusz.loskot.net

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