Index: Doc/library/operator.rst =================================================================== --- Doc/library/operator.rst (Revision 60133) +++ Doc/library/operator.rst (Arbeitskopie) @@ -532,6 +532,17 @@ [('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)] +.. function:: methodcaller(name[, args...]) + + Return a callable object that calls the method *name* on its operand. If + additional arguments and/or keyword arguments are given, they will be given + to the method as well. After ``f = methodcaller('name')``, the call ``f(b)`` + returns ``b.name()``. After ``f = methodcaller('name', 'foo', bar=1)``, the + call ``f(b)`` returns ``b.name('foo', bar=1)``. + + .. versionadded:: 2.6 + + .. _operator-map: Mapping Operators to Functions Index: Lib/test/test_operator.py =================================================================== --- Lib/test/test_operator.py (Revision 60142) +++ Lib/test/test_operator.py (Arbeitskopie) @@ -420,6 +420,24 @@ self.assertEqual(operator.itemgetter(2,10,5)(data), ('2', '10', '5')) self.assertRaises(TypeError, operator.itemgetter(2, 'x', 5), data) + def test_methodcaller(self): + self.assertRaises(TypeError, operator.methodcaller) + class A: + def foo(self, *args, **kwds): + return args[0] + args[1] + def bar(self, f=42): + return f + a = A() + f = operator.methodcaller('foo') + self.assertRaises(IndexError, f, a) + f = operator.methodcaller('foo', 1, 2) + self.assertEquals(f(a), 3) + f = operator.methodcaller('bar') + self.assertEquals(f(a), 42) + self.assertRaises(TypeError, f, a, a) + f = operator.methodcaller('bar', f=5) + self.assertEquals(f(a), 5) + def test_inplace(self): class C(object): def __iadd__ (self, other): return "iadd" Index: Modules/operator.c =================================================================== --- Modules/operator.c (Revision 60133) +++ Modules/operator.c (Arbeitskopie) @@ -575,6 +575,139 @@ attrgetter_new, /* tp_new */ 0, /* tp_free */ }; + + +/* methodcaller object **********************************************************/ + +typedef struct { + PyObject_HEAD + PyObject *name; + PyObject *args; + PyObject *kwds; +} methodcallerobject; + +static PyTypeObject methodcaller_type; + +static PyObject * +methodcaller_new(PyTypeObject *type, PyObject *args, PyObject *kwds) +{ + methodcallerobject *mc; + PyObject *name, *newargs; + + if (PyTuple_GET_SIZE(args) < 1) { + PyErr_SetString(PyExc_TypeError, "methodcaller needs at least " + "one argument, the method name"); + return NULL; + } + + /* create methodcallerobject structure */ + mc = PyObject_GC_New(methodcallerobject, &methodcaller_type); + if (mc == NULL) + return NULL; + + newargs = PyTuple_GetSlice(args, 1, PyTuple_GET_SIZE(args)); + if (newargs == NULL) { + Py_DECREF(mc); + return NULL; + } + mc->args = newargs; + + name = PyTuple_GET_ITEM(args, 0); + Py_INCREF(name); + mc->name = name; + + Py_XINCREF(kwds); + mc->kwds = kwds; + + PyObject_GC_Track(mc); + return (PyObject *)mc; +} + +static void +methodcaller_dealloc(methodcallerobject *mc) +{ + PyObject_GC_UnTrack(mc); + Py_XDECREF(mc->name); + Py_XDECREF(mc->args); + Py_XDECREF(mc->kwds); + PyObject_GC_Del(mc); +} + +static int +methodcaller_traverse(methodcallerobject *mc, visitproc visit, void *arg) +{ + Py_VISIT(mc->args); + Py_VISIT(mc->kwds); + return 0; +} + +static PyObject * +methodcaller_call(methodcallerobject *mc, PyObject *args, PyObject *kw) +{ + PyObject *method, *obj, *result; + + if (!PyArg_UnpackTuple(args, "methodcaller", 1, 1, &obj)) + return NULL; + method = PyObject_GetAttr(obj, mc->name); + if (method == NULL) + return NULL; + result = PyObject_Call(method, mc->args, mc->kwds); + Py_DECREF(method); + return result; +} + +PyDoc_STRVAR(methodcaller_doc, +"methodcaller(name, ...) --> methodcaller object\n\ +\n\ +Return a callable object that calls the given method on its operand.\n\ +After, f = methodcaller('name'), the call f(r) returns r.name().\n\ +After, g = methodcaller('name', 'date', foo=1), the call g(r) returns\n\ +r.name('date', foo=1)."); + +static PyTypeObject methodcaller_type = { + PyVarObject_HEAD_INIT(NULL, 0) + "operator.methodcaller", /* tp_name */ + sizeof(methodcallerobject), /* tp_basicsize */ + 0, /* tp_itemsize */ + /* methods */ + (destructor)methodcaller_dealloc, /* tp_dealloc */ + 0, /* tp_print */ + 0, /* tp_getattr */ + 0, /* tp_setattr */ + 0, /* tp_compare */ + 0, /* tp_repr */ + 0, /* tp_as_number */ + 0, /* tp_as_sequence */ + 0, /* tp_as_mapping */ + 0, /* tp_hash */ + (ternaryfunc)methodcaller_call, /* tp_call */ + 0, /* tp_str */ + PyObject_GenericGetAttr, /* tp_getattro */ + 0, /* tp_setattro */ + 0, /* tp_as_buffer */ + Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */ + methodcaller_doc, /* tp_doc */ + (traverseproc)methodcaller_traverse, /* tp_traverse */ + 0, /* tp_clear */ + 0, /* tp_richcompare */ + 0, /* tp_weaklistoffset */ + 0, /* tp_iter */ + 0, /* tp_iternext */ + 0, /* tp_methods */ + 0, /* tp_members */ + 0, /* tp_getset */ + 0, /* tp_base */ + 0, /* tp_dict */ + 0, /* tp_descr_get */ + 0, /* tp_descr_set */ + 0, /* tp_dictoffset */ + 0, /* tp_init */ + 0, /* tp_alloc */ + methodcaller_new, /* tp_new */ + 0, /* tp_free */ +}; + + /* Initialization function for the module (*must* be called initoperator) */ PyMODINIT_FUNC @@ -597,4 +730,9 @@ return; Py_INCREF(&attrgetter_type); PyModule_AddObject(m, "attrgetter", (PyObject *)&attrgetter_type); + + if (PyType_Ready(&methodcaller_type) < 0) + return; + Py_INCREF(&methodcaller_type); + PyModule_AddObject(m, "methodcaller", (PyObject *)&methodcaller_type); }