[3.13] gh-142495: Make `defaultdict` keep existed value when racing with `missing` (GH-142668) (GH-142858)

(cherry picked from commit a0434075108efe6acdfba34f42545f4d80ac9a5e)

Co-authored-by: Edward Xu <xuxiangad@gmail.com>

Serhiy Storchaka committed 5mo ago

9361207bc2d198a10f7b9b6edda98f7da328cf93

Parent: e07cda3

Committed by GitHub <noreply@github.com> on 12/17/2025, 8:40:47 AM

[3.13] gh-142495: Make `defaultdict` keep existed value when racing with `__missing__` (GH-142668) (GH-142858)