as alternative API to PyLong_GetSign().

It seems, C-API WG is positive on this, see capi-workgroup/decisions#29. This issue will track implementation.

Linked PRs

• gh-126061: Add PyLong_IsPositive/Zero/Negative() functions #126065
• gh-126061: add PyLong_IsPositive/Negative/Zero/GetSign functions to refcounts.dat #126788