| msg48529 - (view) |
Author: Greg Couch (gregcouch) |
Date: 2005-06-28 18:57 |
| Non-heap types, aka builtin types, cannot have their attributes changed by Python code -- see Objects/typeobject.c: type_setattro(). This limitation is good for Python's core builtin types (int, float, list, dict, ...), but not necessarily for non-heap types in extension modules. The attached patch allows for non-heap types to mutate iff the Py_TPFLAGS_MUTABLE_BUILTIN flag is set. |
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| msg48530 - (view) |
Author: Martin v. Löwis (loewis) *  |
Date: 2005-07-11 16:44 |
| Logged In: YES user_id=21627 Why can't you create such a type as a heap type? |
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| msg48531 - (view) |
Author: Greg Couch (gregcouch) |
Date: 2005-07-15 07:26 |
| Logged In: YES user_id=131838 One reason that the type wasn't a heap type was because I didn't find an example in the Python documentation. And because when I was looking through typeobject.c, I saw code, like type_get_doc(), that ignores the (tp_doc) slot when it is a heap type -- exactly what I don't want (looking closer, it may be the only one). I also like most of the restrictions a non-heap type has, like being unable to change its name. So if heap types are as fast as non-heap types, then I have no objection to switching. I'm also concerned about the additional startup time switching to heap types would cost since I currently have 75 types in my module. The python code that prompted this patch was code that reached in and added extra keyword arguments to a method, sort of like a decorator, for additional bookkeeping. Subclassing is out because the C (C++) object factory function only returns the instances of the original type. |
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| msg82391 - (view) |
Author: Greg Couch (gregcouch) |
Date: 2009-02-18 00:04 |
| FYI, I was able to work around this and use an unmodified Python by subtyping type and overriding the setattr method as shown below. It's a lot messier than patching Python. static int Mutable_SetAttr(PyObject *obj, PyObject *name, PyObject *value) { // Can't just call PyObject_GenericSetAttr because // we need to able to update the __str__ slot as well. PyTypeObject *type = reinterpret_cast<PyTypeObject*>(obj); type->tp_flags |= Py_TPFLAGS_HEAPTYPE; int result = PyType_Type.tp_setattro(obj, name, value); type->tp_flags &= ~Py_TPFLAGS_HEAPTYPE; return result; } |
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| msg162994 - (view) |
Author: Terry J. Reedy (terry.reedy) * |
Date: 2012-06-16 21:23 |
| Greg, I am closing this because you seem to have found an alternate solution and have dropped the issue. If you do want to pursue a change for 3.4, I suggest you refresh your patch and post to python-ideas (new list since you posted this). As a limited resource, flags are not casually added, and I know another request was recently denied on pydev. |
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