Bug report

In pdb,ll will clear the local variable change.

defmain():a=1breakpoint()print(a)main()

->print(a)(Pdb)pa1(Pdb) !a=2(Pdb)pa2(Pdb)ll1defmain():2a=13breakpoint()4->print(a)(Pdb)pa1(Pdb)s1--Return--

As you can tell,a was changed through!a = 2 but it was reverted afterll.print(a) also prints the unmodified value. Withoutll, everything works fine.

The reason lies ingetsourcelines inpdb.py. In that function, it tried to accessobj.f_locals, which will refresh the dict withPyFrame_FastToLocalsWithError as it's a property now.

ifinspect.isframe(obj)andobj.f_globalsisobj.f_locals:

As a result, the local variable changes will be erased.

The original reason to check ifobj.f_globals is obj.f_locals is to check whetherobj is an module frame. Now that it has side effects to pdb, we can do the check with:

ifinspect.isframe(obj)andobj.f_code.co_name=="<module>":

It might not be the most delicate way, but I can't think of a situation where this won't work.

I did this change locally and I have confirmed:

1. ./python -m test -j3 passed
2. The original bug is fixed
3. ll still prints the full file for module frame

I'll make a PR soon and please let me know if there are any concerns about the fix.

Your environment

• CPython versions tested on: 3.11.1
• Operating system and architecture: Ubuntu 20.04

Linked PRs

• GH-101673: Fix pdb bug that local variable changes lost after longlist #101674
• [3.11] GH-101673: Fix pdb bug where local variable changes are lost after longlist (GH-101674) #102632
• [3.10] GH-101673: Fix pdb bug where local variable changes are lost after longlist (#101674) #102633