> Why not combine my patch and Serhiy's?  First we check if left & right are both longs.  Then we check if they are unicode (for +).  And then we have a fastpath for floats.

See my comment on Serhiy's patch. Maybe we can start by check that the type of both operands are the same, and then use PyLong_CheckExact and PyUnicode_CheckExact.

Using such design, we may add a _PyFloat_Add(). But the next question is then the overhead on the "slow" path, which requires a benchmark too! For example, use a subtype of int.