[Python-Dev] A bit faster access to module attributes (original) (raw)

Wiktor Sadowski Wiktor Sadowski" <art@wiktorsadowski.com
Tue, 1 Jul 2003 03:40:23 +0200

Python module calls PyObject_GenericGetAttr/PyObject_GenericSetAttr pair to do attribute lookup. (moduleobject.c,object.c)

IMO it adds unnecessary overhead, and could be replaced with a bit simplified functions.

[1] To get an object's dictionary _PyObject_GetDictPtr function is used (inlined in PyObject_GenericGetAttr). But in module case we can get the dictionary without any call: PyObject *dict = ((PyModuleObject *)obj)->md_dict;

[2] If module(tp)->tp_dict == NULL PyType_Ready is called in PyObject_GenericGetAttr. Well , I am not sure if all this stuff added to module type with PyType_Ready is really necessary but instead of calling _PyType_Lookup machinery a simple:

if (strcmp(PyString_AS_STRING(name/attr/),"dict")==0) (+ PyErr_SetString(PyExc_TypeError, "readonly attribute") for setattr function)

could be used to access readonly module "dict" attribute.

The solution I am proposing is probably less elegant than PyObject_GenericGetAttr/PyObject_GenericSetAttr but if it could speed up Python a bit ?

If someone would like to test such modified modules, binaries for Windows of my small C extension - modeler.pyd are available at: http://www.wiktorsadowski.com/Python

Importing modeler will replace module tp_getattro/ tp_setattro with new functions, and will enable faster access to modules' attributes. (if no other modeler features are used)

Regards Wiktor Sadowski

A new getattr for module tp_getattro could look like this: (the settattr could be simplified as well)

PyObject * PyObject_ModuleGetAttr(PyObject *obj, PyObject *name) {

PyObject *res = NULL; PyTypeObject *tp = obj->ob_type; PyObject *dict = ((PyModuleObject *)obj)->md_dict;

/string check stuff - no changes/

if (dict == NULL) { /* it shouldn't happen! / ((PyModuleObject )obj)->md_dict=Py_DictNew();/?/ }

if (strcmp(PyString_AS_STRING(name),"dict")==0){ Py_INCREF(dict); return dict; }

res = PyDict_GetItem(dict, name); if (res != NULL) { Py_INCREF(res); Py_XDECREF(name); return res; }

PyErr_Format(PyExc_AttributeError, "'%.50s' object has no attribute '%.400s'", tp->tp_name, PyString_AS_STRING(name));

}