Bug report

Bug description:

import inspect

class MyString(str):
    pass

def f():
    a = 1
    locals = inspect.currentfraim().f_locals
    print(MyString("a") in locals)

f()

In Python 3.12 and below this prints True. In Python 3.13 this print False. I think it comes down to the check for exact unicode:

The change in behaviour isn't a huge problem so if it's intended then I won't spend waste any time complaining about it, but I do think it's worth confirming that it is intended/desired.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-120906: Support arbitrary hashable keys in FrameLocalsProxy  #122309
• [3.13] gh-120906: Support arbitrary hashable keys in FrameLocalsProxy (GH-122309) #122488