What is the most efficient way of serializing a numpy array using simplejson?
I'd use simplejson.dumps(somearray.tolist()) as the most convenient approach (if I was still using simplejson at all, which implies being stuck with Python 2.5 or earlier; 2.6 and later have a standard library module json which works the same way, so of course I'd use that if the Python release in use supported it;-).
In a quest for greater efficiency, you could subclass json.JSONEncoder (in json; I don't know if the older simplejson already offered such customization possibilities) and, in the default method, special-case instances of numpy.array by turning them into list or tuples "just in time". I kind of doubt you'd gain enough by such an approach, in terms of performance, to justify the effort, though.