pathlib: Path.iterdir() is surprisingly not streaming

Bug report

Suprisingly (contrary to its name and being a generator), Path.iterdir() does not stream directory entries:

It reads all directory entries into memory before yielding the first entry.

This can cause excessive memory usage when "iterating" over very large directories.

Users would expect by default that .iterdir() operates in a streaming way, like UNIX find or readdir(), streaming e.g. the results of the underlying system calls such as getdents64() on Linux.

But it does entries = list(scandir_it) instead:

https://github.com/python/cpython/blob/c419af9e277bea7dd78f4defefc752fe93b0b8ec/Lib/pathlib/__init__.py#L835-L843

This should be documented, and can hopefully be fixed without too much breakage.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Related issues

• https://github.com/python/cpython/issues/129871

Linked PRs

• gh-136060

Commencez par Lib/pathlib/init.py, dans l’implémentation liée de Path.iterdir(), autour des lignes 835-843, puis examinez l’issue associée 129871 et la PR liée 136060. Confirmez le comportement d’itération attendu ainsi que les exigences de compatibilité ; le travail est terminé lorsque le comportement de streaming de l’issue est pris en charge et couvert par les tests pathlib pertinents.