On Fri, Feb 26, 2016 at 4:08 PM, Sven R. Kunze <srku...@mail.de> wrote: > Python sometimes seems not to hop back and forth between C and Python code. > Can somebody explain this?
Normally a C extension would call PySequence_SetItem, which would call the type's sq_ass_item, which for MyList is slot_sq_ass_item. The latter function bridges the CPython and Python sides by binding and calling the overridden __setitem__ method. However, the _heapq extension module uses `PyList_SET_ITEM(heap, 0, lastelt)`. This macro expands to `((PyListObject *)(heap))->ob_item[0] = lastelt`. This directly modifies the internal ob_item array of the list, so the overridden __setitem__ method is never called. I presume it was implemented like this with performance in mind, but I don't know whether or not that justifies the loss of generality. -- https://mail.python.org/mailman/listinfo/python-list
