The current Python C API PyTuple_New() to build a tuple has multiple flaws:
- The Python tuple object is immediately tracked by the GC, whereas its items are initialized to NULL (inconsistent tuple)
- The PyTuple_SET_ITEM() function must only used on a tuple while is being created
I propose adding a new internal C API to build a tuple: _PyTupleBuilder.
- User of the API doesn't access the tuple directly but uses higher API
- Over-allocate the tuple (by 25%) to reduce the number of _PyTuple_Resize() calls
- _PyTupleBuild_Append() grows the tuple if needed
- _PyTupleBuild_AppendUnsafe() is a thin wrapper to PyTuple_SET_ITEM()
- Only track the tuple once its fully initialized: correct size, all items are set
- Less error-prone API
Later, once we will consider this API stable, we can add it to the public C API and deprecate the old API to create an incomplete tuple:
- PyTuple_New()
- PyTuple_SetItem()
- PyTuple_SET_ITEM()
- _PyTuple_Resize()
See capi-workgroup/problems#56 for details on problems caused by API which let creating incomplete/inconsistent objects.
Linked PRs
The current Python C API PyTuple_New() to build a tuple has multiple flaws:
I propose adding a new internal C API to build a tuple: _PyTupleBuilder.
Later, once we will consider this API stable, we can add it to the public C API and deprecate the old API to create an incomplete tuple:
See capi-workgroup/problems#56 for details on problems caused by API which let creating incomplete/inconsistent objects.
Linked PRs