gh-141510, PEP 814: Add built-in frozendict type by vstinner · Pull Request #144757 · python/cpython · GitHub

Add TYPE_FROZENDICT to the marshal module.

Add C API functions:

PyAnyDict_Check()
PyAnyDict_CheckExact()
PyFrozenDict_Check()
PyFrozenDict_CheckExact()
PyFrozenDict_New()

Add PyFrozenDict_Type C type.

Issue: PEP 814: Add built-in frozendict type #141510

📚 Documentation preview 📚: https://cpython-previews--144757.org.readthedocs.build/en/144757/c-api/dict.html#frozen-dictionary-objects

Add TYPE_FROZENDICT to the marshal module. Add C API functions: * PyAnyDict_Check() * PyAnyDict_CheckExact() * PyFrozenDict_Check() * PyFrozenDict_CheckExact() * PyFrozenDict_New() Add PyFrozenDict_Type C type.

cc @corona10

Fix also indentation.

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Maybe same opinion with @kumaraditya303 we can avoid a lot of critical section if dict is frozen dict.

I agree, but I would prefer to make such "optimization" change in a separated PR.

Do we have to use atomic operation for frozendict?

No, we can skip the atomic operation for frozendict.

It uses relaxed atomic so it compiles to simple loads so avoiding it has no real benefit.

len(frozendict) has been optimized by #144913.

I think that we can make frozendict_lenth

I propose to make such optimization in a separated PR.

Still perfer to make frozendict_subscript, but let's do it at the separate PR.

We should notice that frozendict is not subclass of dict to follow SC feedback

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Document frozendict after lazy import.

We might take this fast-path for frozendict as well. It's just a missed optimization opportunity.

@corona10: Add it to the optimization TODO list :-)

Yeah I will take a look at it

The current implementation creates an actual frozenset object which emits surprising error messages:

>>> hash(frozendict(x=[]))
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    hash(frozendict(x=[]))
    ~~~~^^^^^^^^^^^^^^^^^^
TypeError: cannot use 'tuple' as a set element (unhashable type: 'list')

We may change the implementation later to not create an actual frozenset, but reuse frozenset hash code instead, to avoid the surprising errors.

I changed the implementation in #144919.

We should notice that frozendict is not subclass of dict to follow SC feedback

Ah right, done.

🤖 New build scheduled with the buildbot fleet by @corona10 for commit 9101b1a 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F144757%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-refleak-buildbots label again.

Let's wait build bot to pass the refleak test :)

Nitpick: I know this does not primarily belong to the PR, but it's such a small change that a new PR wouldn't make sense for these small "typos".

Co-authored-by: Adam Johnson <me@adamj.eu>

Let's wait build bot to pass the refleak test :)

Tests passed successfully on Refleaks buildbots:

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Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Add also a title in Doc/library/stdtypes.rst.

@hugovk: I modified a few more titles in the C API doc and the Python doc to use sentence case for headers.

lgtm with current implementations , I will soon create PRs for removing unneeded overhead from my side.

Couple of nitpicks.

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Co-authored-by: Benedikt Johannes <benedikt.johannes.hofer@gmail.com>

I merged my PR. Thank you very much for all your reviews!

Add TYPE_FROZENDICT to the marshal module. Add C API functions: * PyAnyDict_Check() * PyAnyDict_CheckExact() * PyFrozenDict_Check() * PyFrozenDict_CheckExact() * PyFrozenDict_New() Add PyFrozenDict_Type C type. Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com> Co-authored-by: Adam Johnson <me@adamj.eu> Co-authored-by: Benedikt Johannes <benedikt.johannes.hofer@gmail.com>

pythongh-141510 , PEP 814: Add built-in frozendict type

bde4379

Add TYPE_FROZENDICT to the marshal module. Add C API functions: * PyAnyDict_Check() * PyAnyDict_CheckExact() * PyFrozenDict_Check() * PyFrozenDict_CheckExact() * PyFrozenDict_New() Add PyFrozenDict_Type C type.

bedevere-app Bot mentioned this pull request Feb 12, 2026

PEP 814: Add built-in frozendict type #141510

Closed

vstinner added 2 commits February 12, 2026 19:25

Document PyFrozenDict_Type in the C API doc

1fb7c5a

Fix test_inspect and test_doctest

fca2e5b

vstinner marked this pull request as ready for review February 13, 2026 07:30

vstinner requested review from AA-Turner, ZeroIntensity, ericsnowcurrently, markshannon, methane and rhettinger as code owners February 13, 2026 07:30

bedevere-app Bot added the awaiting core review label Feb 13, 2026

Complete the documentation

99b291c

vstinner mentioned this pull request Feb 13, 2026

[WIP] gh-141510: PEP 814: Add built-in frozendict type #141508

Closed

Fix doc warnings

5e4a284

Fix also indentation.

corona10 self-requested a review February 13, 2026 10:07

hugovk reviewed Feb 13, 2026

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5c0c6f1

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

kumaraditya303 reviewed Feb 13, 2026

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Comment thread Objects/dictobject.c

corona10 reviewed Feb 13, 2026

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vstinner and others added 3 commits February 13, 2026 15:46

Apply suggestion from @hugovk

8d4ed14

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Move the What's New entry

c770613

Document frozendict after lazy import.

Revert _PyDict_LoadBuiltinsFromGlobals() change

6dfec48

vstinner commented Feb 13, 2026

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Document that frozendict is not a dict subclass

9101b1a

corona10 added the 🔨 test-with-refleak-buildbots Test PR w/ refleak buildbots; report in status section label Feb 14, 2026

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Comment thread Doc/library/stdtypes.rst

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Comment thread Doc/library/stdtypes.rst Outdated

Update Doc/library/stdtypes.rst

e845b2b

Co-authored-by: Adam Johnson <me@adamj.eu>

hugovk reviewed Feb 16, 2026

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vstinner and others added 2 commits February 16, 2026 13:01

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Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

doc: use sentence case for headers

258b3df

Add also a title in Doc/library/stdtypes.rst.

corona10 approved these changes Feb 16, 2026

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sergey-miryanov reviewed Feb 16, 2026

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Comment thread Objects/dictobject.c

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vstinner and others added 2 commits February 16, 2026 21:33

Add tests on repr(frozendict)

09abcf5

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3653eeb

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

benediktjohannes reviewed Feb 16, 2026

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Co-authored-by: Benedikt Johannes <benedikt.johannes.hofer@gmail.com>

vstinner merged commit 696cdfc into python:main Feb 17, 2026
47 checks passed

vstinner deleted the frozendict_base branch February 17, 2026 09:54

bedevere-app Bot removed the awaiting merge label Feb 17, 2026

savannahostrowski mentioned this pull request Feb 18, 2026

dict_traverse crash during PGO training on Windows with JIT enabled #144970

Closed

                           mp->ma_values == NULL &&
-                          (mp->ma_used >= (mp->ma_keys->dk_nentries * 2) / 3))
+                          (mp->ma_used >= (mp->ma_keys->dk_nentries * 2) / 3) &&
+                          !frozendict)

                   }
-                  if (PyDict_CheckExact(d)) {
+                  if (PyAnyDict_CheckExact(d)) {

               dict_length(PyObject *self)
               {
-                  return FT_ATOMIC_LOAD_SSIZE_RELAXED(((PyDictObject *)self)->ma_used);
+                  return GET_USED(_PyAnyDict_CAST(self));

+              };
+              static PyMappingMethods frozendict_as_mapping = {
+                  .mp_length = dict_length,

+                  if (items == NULL) {
+                      return -1;
+                  }
+                  PyObject *frozenset = PyFrozenSet_New(items);

gh-141510, PEP 814: Add built-in frozendict type by vstinner · Pull Request #144757 · python/cpython · GitHub

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gh-141510, PEP 814: Add built-in frozendict type - #144757

gh-141510, PEP 814: Add built-in frozendict type#144757vstinner merged 16 commits intopython:mainpython/cpython:mainfrom vstinner:frozendict_basevstinner/cpython:frozendict_baseCopy head branch name to clipboard

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gh-141510, PEP 814: Add built-in frozendict type#144757
vstinner merged 16 commits into
python:mainfrom
vstinner:frozendict_base

vstinner commented Feb 12, 2026 •
edited by hugovk
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