bpo-40890: Add `mapping` property to dict views (GH-20749)

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Dennis Sweeney 2020-06-12 13:19:25 -04:00 committed by GitHub
parent 0d3350daa8
commit 3ee0e48b03
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5 changed files with 58 additions and 3 deletions

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@ -4622,6 +4622,12 @@ support membership tests:
.. versionchanged:: 3.8
Dictionary views are now reversible.
.. describe:: dictview.mapping
Return a :class:`types.MappingProxyType` that wraps the original
dictionary to which the view refers.
.. versionadded:: 3.10
Keys views are set-like since their entries are unique and hashable. If all
values are hashable, so that ``(key, value)`` pairs are unique and hashable,
@ -4661,6 +4667,12 @@ An example of dictionary view usage::
>>> keys ^ {'sausage', 'juice'}
{'juice', 'sausage', 'bacon', 'spam'}
>>> # get back a read-only proxy for the original dictionary
>>> values.mapping
mappingproxy({'eggs': 2, 'sausage': 1, 'bacon': 1, 'spam': 500})
>>> values.mapping['spam']
500
.. _typecontextmanager:

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@ -74,6 +74,11 @@ New Features
number of ones in the binary expansion of a given integer, also known
as the population count. (Contributed by Niklas Fiekas in :issue:`29882`.)
* The views returned by :meth:`dict.keys`, :meth:`dict.values` and
:meth:`dict.items` now all have a ``mapping`` attribute that gives a
:class:`types.MappingProxyType` object wrapping the original
dictionary. (Contributed by Dennis Sweeney in :issue:`40890`.)
Other Language Changes
======================

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@ -105,6 +105,26 @@ class DictTest(unittest.TestCase):
self.assertRaises(TypeError, d.items, None)
self.assertEqual(repr(dict(a=1).items()), "dict_items([('a', 1)])")
def test_views_mapping(self):
mappingproxy = type(type.__dict__)
class Dict(dict):
pass
for cls in [dict, Dict]:
d = cls()
m1 = d.keys().mapping
m2 = d.values().mapping
m3 = d.items().mapping
for m in [m1, m2, m3]:
self.assertIsInstance(m, mappingproxy)
self.assertEqual(m, d)
d["foo"] = "bar"
for m in [m1, m2, m3]:
self.assertIsInstance(m, mappingproxy)
self.assertEqual(m, d)
def test_contains(self):
d = {}
self.assertNotIn('a', d)

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@ -0,0 +1 @@
Each dictionary view now has a ``mapping`` attribute that provides a :class:`types.MappingProxyType` wrapping the original dictionary. Patch contributed by Dennis Sweeney.

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@ -4122,6 +4122,23 @@ _PyDictView_New(PyObject *dict, PyTypeObject *type)
return (PyObject *)dv;
}
static PyObject *
dictview_mapping(PyObject *view)
{
assert(view != NULL);
assert(PyDictKeys_Check(view)
|| PyDictValues_Check(view)
|| PyDictItems_Check(view));
PyObject *mapping = (PyObject *)((_PyDictViewObject *)view)->dv_dict;
return PyDictProxy_New(mapping);
}
static PyGetSetDef dictview_getset[] = {
{"mapping", (getter)dictview_mapping, (setter)NULL,
"dictionary that this view refers to", NULL},
{0}
};
/* TODO(guido): The views objects are not complete:
* support more set operations
@ -4635,7 +4652,7 @@ PyTypeObject PyDictKeys_Type = {
(getiterfunc)dictkeys_iter, /* tp_iter */
0, /* tp_iternext */
dictkeys_methods, /* tp_methods */
0,
.tp_getset = dictview_getset,
};
static PyObject *
@ -4741,7 +4758,7 @@ PyTypeObject PyDictItems_Type = {
(getiterfunc)dictitems_iter, /* tp_iter */
0, /* tp_iternext */
dictitems_methods, /* tp_methods */
0,
.tp_getset = dictview_getset,
};
static PyObject *
@ -4822,7 +4839,7 @@ PyTypeObject PyDictValues_Type = {
(getiterfunc)dictvalues_iter, /* tp_iter */
0, /* tp_iternext */
dictvalues_methods, /* tp_methods */
0,
.tp_getset = dictview_getset,
};
static PyObject *