Ref. https://bugs.python.org/issue43908, I've compiled a list of types that have been converted to heap types. I've posted it on Discourse for readability: https://discuss.python.org/t/list-of-built-in-types-converted-to-heap-types/... Note: for now, I didn't bother to trace PyType_Spec variable names to complete type names. Hope it's not too much of a problem. Erlend Here's the plain text version: 0b858cdd5d 2021-01-04 Modules/cjkcodecs/multibytecodec.c - multibytecodec_spec - encoder_spec - decoder_spec - reader_spec - writer_spec c8a87addb1 2021-01-04 Modules/pyexpat.c - _xml_parse_type_spec 75bf107c62 2021-01-02 Modules/arraymodule.c - array_spec - arrayiter_spec dd39123970 2020-12-29 Modules/_functoolsmodule.c - partial_type_spec - keyobject_type_spec - lru_list_elem_type_spec - lru_cache_type_spec 6104013838 2020-12-18 Modules/_threadmodule.c - lock_type_spec - rlock_type_spec - local_dummy_type_spec - local_type_spec a6109ef68d 2020-11-20 Modules/_sre.c - pattern_spec - match_spec - scanner_spec 5c36da78d7 2020-11-20 Modules/_ssl.c - PySSLSocket_spec - PySSLContext_spec - PySSLMemoryBIO_spec - PySSLSession_spec 01c6aa43dc 2020-11-07 Modules/_queuemodule.c - simplequeue_spec 74b4eda98b 2020-11-03 Modules/mmapmodule.c - mmap_object_spec c8c4200b65 2020-10-26 Modules/unicodedata.c - ucd_type_spec 256e54acdb 2020-10-01 Modules/_sqlite - connection_spec - cursor_spec 9031bd4fa4 2020-10-01 Modules/_sqlite - row_spec - stmt_spec cb6db8b6ae 2020-09-29 Modules/_sqlite - type_spec (PrepareProtocolType) a937ab45d6 2020-09-27 Modules/_sqlite - node_spec - cache_spec 83de110dce 2020-09-23 Modules/_lsprof.c - _lsprof_profiler_type_spec 52a2df135c 2020-09-08 Modules/sha256module.c - sha224_type_spec - sha256_type_spec 2aabc3200b 2020-09-07 Modules/overlapped.c - overlapped_type_spec 63f102fe07 2020-09-06 Modules/md5module.c Modules/sha1module.c Modules/sha512module.c - md5_type_spec - sha1_type_spec - sha512_sha384_type_spec - sha512_sha512_type_spec 31967fd8d0 2020-08-27 Modules/_operator.c - itemgetter_type_spec - attrgetter_type_spec - methodcaller_type_spec e087f7cd43 2020-08-13 Modules/_winapi.c - winapi_overlapped_type_spec 1937edd376 2020-06-23 Modules/_lzmamodule.c - lzma_compressor_type_spec - lzma_decompressor_type_spec ec68918795 2020-06-20 Modules/_bz2module.c - bz2_compressor_type_spec - bz2_decompressor_type_spec c4862e333a 2020-06-17 Modules/_gdbmmodule.c - gdbmtype_spec bf69a8f99f 2020-06-16 Modules/_dbmmodule.c - dbmtype_spec d5b3f6b7f9 2020-05-16 Modules/_hashopenssl.c - EVPXOFtype_spec 53e4c91725 2020-03-30 Modules/_abc.c - _abc_data_type_spec 33f15a16d4 2020-03-27 Modules/_json.c - PyScannerType_spec - PyEncoderType_spec b3966639d2 2019-11-05 Modules/posixmodule.c - DirEntryType_spec - ScandirIteratorType_spec df69e75edc 2019-09-25 Modules/_hashopenssl.c - EVPtype_spec f919054e53 2019-09-14 Modules/selectmodule.c - devpoll_Type_spec - kqueue_event_Type_spec - poll_Type_spec - pyEpoll_Type_spec - kqueue_queue_Type_spec 04f0bbfbed 2019-09-13 Modules/_randommodule.c - Random_Type_spec ac46eb4ad6 2019-09-11 Python/Python-ast.c - AST_type_spec - AST_type_spec a1ffad0719 2019-09-10 Modules/zlibmodule.c - Comptype_spec - Decomptype_spec 4f384af067 2019-09-10 Modules/_struct.c - unpackiter_type_spec - PyStructType_spec 11dc6c311d 2012-10-14 Modules/_tkinter.c - PyTclObject_Type_spec - Tktt_Type_spec - Tkapp_Type_spec 3b36fb1f53 2012-06-22 Modules/_ssl.c - sslerror_type_spec bc07cb883e 2012-06-14 Modules/_curses_panel.c - PyCursesPanel_Type_spec