Make properties discoverable from Python:
- property() now takes 4 keyword arguments: fget, fset, fdel, doc.
Note that the real purpose of the 'f' prefix is to make fdel fit in
('del' is a keyword, so can't used as a keyword argument name).
- These map to visible readonly attributes 'fget', 'fset', 'fdel',
and '__doc__' in the property object.
- fget/fset/fdel weren't discoverable from Python before.
- __doc__ is new, and allows to associate a docstring with a property.
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index fdf2a41..5bd837e 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1364,7 +1364,7 @@
self.__x = value
def delx(self):
del self.__x
- x = property(getx, setx, delx)
+ x = property(getx, setx, delx, doc="I'm the x property.")
a = C()
verify(not hasattr(a, "x"))
a.x = 42
@@ -1378,6 +1378,32 @@
## C.x.__set__(a)
## verify(not hasattr(a, "x"))
+ raw = C.__dict__['x']
+ verify(isinstance(raw, property))
+
+ attrs = dir(raw)
+ verify("__doc__" in attrs)
+ verify("fget" in attrs)
+ verify("fset" in attrs)
+ verify("fdel" in attrs)
+
+ verify(raw.__doc__ == "I'm the x property.")
+ verify(raw.fget is C.__dict__['getx'])
+ verify(raw.fset is C.__dict__['setx'])
+ verify(raw.fdel is C.__dict__['delx'])
+
+ for attr in "__doc__", "fget", "fset", "fdel":
+ try:
+ setattr(raw, attr, 42)
+ except TypeError, msg:
+ if str(msg).find('readonly') < 0:
+ raise TestFailed("when setting readonly attr %r on a "
+ "property, got unexpected TypeError "
+ "msg %r" % (attr, str(msg)))
+ else:
+ raise TestFailed("expected TypeError from trying to set "
+ "readonly %r attr on a property" % attr)
+
def supers():
if verbose: print "Testing super..."
@@ -1884,7 +1910,7 @@
zz = ZZ(1.0000003)
verify(zz == 1+0j)
verify(1+0j == zz)
-
+
class classic:
pass
for base in (classic, int, object, list):
diff --git a/Misc/NEWS b/Misc/NEWS
index 7e0234f..3691616 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -3,6 +3,12 @@
Core
+- property() now takes 4 keyword arguments: fget, fset, fdel and doc.
+ These map to readonly attributes 'fget', 'fset', 'fdel', and '__doc__'
+ in the constructed property object. fget, fset and fdel weren't
+ discoverable from Python in 2.2a3. __doc__ is new, and allows to
+ associate a docstring with a property.
+
- file.writelines() now accepts any iterable object producing strings.
- PyUnicode_FromEncodedObject() now works very much like
diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index 7be1074..fea67f3 100644
--- a/Objects/descrobject.c
+++ b/Objects/descrobject.c
@@ -873,9 +873,11 @@
/*
class property(object):
- def __init__(self, get=None, set=None):
- self.__get = get
- self.__set = set
+ def __init__(self, fget=None, fset=None, fdel=None, doc=None):
+ self.__get = fget
+ self.__set = fset
+ self.__del = fdel
+ self.__doc__ = doc
def __get__(self, inst, type=None):
if self.__get is None:
@@ -885,26 +887,42 @@
return self.__get(inst)
def __set__(self, inst, value):
- if self.__set is None:
- raise AttributeError, "unsettable attribute"
- return self.__set(inst, value)
+ if value is None:
+ if self.__del is None:
+ raise AttributeError, "can't delete attribute"
+ return self.__del(inst)
+ else:
+ if self.__set is None:
+ raise AttributeError, "can't set attribute"
+ return self.__set(inst, value)
*/
typedef struct {
PyObject_HEAD
- PyObject *get;
- PyObject *set;
- PyObject *del;
+ PyObject *prop_get;
+ PyObject *prop_set;
+ PyObject *prop_del;
+ PyObject *prop_doc;
} propertyobject;
+static PyMemberDef property_members[] = {
+ {"fget", T_OBJECT, offsetof(propertyobject, prop_get), READONLY},
+ {"fset", T_OBJECT, offsetof(propertyobject, prop_set), READONLY},
+ {"fdel", T_OBJECT, offsetof(propertyobject, prop_del), READONLY},
+ {"__doc__", T_OBJECT, offsetof(propertyobject, prop_doc), READONLY},
+ {0}
+};
+
+
static void
property_dealloc(PyObject *self)
{
propertyobject *gs = (propertyobject *)self;
- Py_XDECREF(gs->get);
- Py_XDECREF(gs->set);
- Py_XDECREF(gs->del);
+ Py_XDECREF(gs->prop_get);
+ Py_XDECREF(gs->prop_set);
+ Py_XDECREF(gs->prop_del);
+ Py_XDECREF(gs->prop_doc);
self->ob_type->tp_free(self);
}
@@ -913,7 +931,7 @@
{
propertyobject *gs = (propertyobject *)self;
- if (gs->get == NULL) {
+ if (gs->prop_get == NULL) {
PyErr_SetString(PyExc_AttributeError, "unreadable attribute");
return NULL;
}
@@ -921,7 +939,7 @@
Py_INCREF(self);
return self;
}
- return PyObject_CallFunction(gs->get, "(O)", obj);
+ return PyObject_CallFunction(gs->prop_get, "(O)", obj);
}
static int
@@ -931,9 +949,9 @@
PyObject *func, *res;
if (value == NULL)
- func = gs->del;
+ func = gs->prop_del;
else
- func = gs->set;
+ func = gs->prop_set;
if (func == NULL) {
PyErr_SetString(PyExc_AttributeError,
value == NULL ?
@@ -954,32 +972,45 @@
static int
property_init(PyObject *self, PyObject *args, PyObject *kwds)
{
- PyObject *get = NULL, *set = NULL, *del = NULL;
+ PyObject *get = NULL, *set = NULL, *del = NULL, *doc = NULL;
+ static char *kwlist[] = {"fget", "fset", "fdel", "doc", 0};
propertyobject *gs = (propertyobject *)self;
- if (!PyArg_ParseTuple(args, "|OOO:property", &get, &set, &del))
+ if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOOO:property",
+ kwlist, &get, &set, &del, &doc))
return -1;
+
if (get == Py_None)
get = NULL;
if (set == Py_None)
set = NULL;
+ if (del == Py_None)
+ del = NULL;
+
Py_XINCREF(get);
Py_XINCREF(set);
Py_XINCREF(del);
- gs->get = get;
- gs->set = set;
- gs->del = del;
+ Py_XINCREF(doc);
+
+ gs->prop_get = get;
+ gs->prop_set = set;
+ gs->prop_del = del;
+ gs->prop_doc = doc;
+
return 0;
}
static char property_doc[] =
-"property([getfunc[, setfunc[, delfunc]]]) -> property attribute\n"
-"Typical use to define a managed attribute x of C instances:\n"
+"property(fget=None, fset=None, fdel=None, doc=None) -> property attribute\n"
+"\n"
+"fget is a function to be used for getting an attribute value, and likewise\n"
+"fset is a function for setting, and fdel a function for del'ing, an\n"
+"attribute. Typical use is to define a managed attribute x:\n"
"class C(object):\n"
" def getx(self): return self.__x\n"
" def setx(self, value): self.__x = value\n"
" def delx(self): del self.__x\n"
-" x = property(getx, setx, delx)";
+" x = property(getx, setx, delx, \"I'm the 'x' property.\")";
PyTypeObject PyProperty_Type = {
PyObject_HEAD_INIT(&PyType_Type)
@@ -1012,7 +1043,7 @@
0, /* tp_iter */
0, /* tp_iternext */
0, /* tp_methods */
- 0, /* tp_members */
+ property_members, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */