def zfill(self, start, stop):
        """Zero-fill the memory at index *start* to *stop*

        *stop* MUST not be smaller than *start*.
        """
        builder = self._builder
        base = self._gep(start)
        end = self._gep(stop)
        intaddr_t = self._context.get_value_type(types.intp)
        size = builder.sub(builder.ptrtoint(end, intaddr_t),
                           builder.ptrtoint(base, intaddr_t))
        cgutils.memset(builder, base, size, ir.IntType(8)(0))
Zero-fill the memory at index *start* to *stop*

        *stop* MUST not be smaller than *start*.
        
numba/cpython/listobj.py