Right now it is implemented as:

Removing unused defining_class: defining_class from clinic has one big adavantage (aside from the fact that it is unused in the first place): it speeds up is_junction call.

The exact benchmark is system-dependent, here are my numbers (note, that I am on macos and always get False as the result).

Setup:

• ./configure --with-pydebug && make -j
• Install pyperf
• pyperf timeit --setup 'import os; d = os.scandir("."); d1 = next(d); d.close()' 'd1.is_junction()'

With defining_class:

(.venv) ~/Desktop/cpython  main ✔                                                      1 ⚠️
» pyperf timeit --setup 'import os; d = os.scandir("."); d1 = next(d); d.close()' 'd1.is_junction()' 
.....................
Mean +- std dev: 46.1 ns +- 0.5 ns

Without:

(.venv) ~/Desktop/cpython  main ✗                                                         
» pyperf timeit --setup 'import os; d = os.scandir("."); d1 = next(d); d.close()' 'd1.is_junction()'
.....................
Mean +- std dev: 25.0 ns +- 0.3 ns

This happens because is_junction def is changed from METH_METHOD|METH_FASTCALL|METH_KEYWORDS to METH_NOARGS.

I have a PR ready.

Linked PRs

• gh-108717: Speedup os.DirEntry.is_junction function #108718