Upon closer inspection, redefine _PyArg_NoKeywords as a macro turned out to be not such a good idea. Other use of _PyArg_NoKeywords are in __new__ and __init__ methods. Create these objects in most cases (except may be slice) is performance critical operation than calling itemgetter, attrgetter or methodcaller object. It is better to add this microoptimization on cases (set and frozenset already have it).