Changing dict.update() calling convention may save a few nanoseconds on d1.update(d2) call, but it will make d1.update(**d2) way slower with a complexity of O(n): d2 must be converted to 2 lists (kwnames and args) and then a new dict should be created.

I don't see the point of micro-optimizing d1.update(d2), if d1.update(**d2) would become way slower.