This package is a Cython wrapper for khash-sets/maps. It brings functionality of khash to Python and Cython and can be used seamlessly in numpy or pandas. Numpy's world is lacking the concept of a (hash-)set. This shortcoming is fixed and efficient (memory- and speedwise compared to pandas) unique and isin are implemented. Python-set/dict have a big memory-footprint. For some datatypes the overhead can be reduced by using khash by factor 4-8.