A point of detail probably, but I suppose that instead of introducing a new method on frame objects, we could allow f_locals to be a writeable attribute.  Setting it to a dictionary would update the value of the local variables.  It's a bit of a hack, but so is the need for an explicit savelocals() method.

A cleaner solution is to have f_locals return a dict-like object instead of a real dict when appropriate, but it takes more efforts to implement.