Heaps of thanks for that Ptrblck, I believe (imbal_class_prop = np.hstack(([0.1] * 5, [1.0] * 5))) divides the classes in only two distribution say either(50%,50%) or 40% and 60% but sill in both distribution number of samples will be same (I mean the all classes having 40% of the total distribution will have equal samples, however, I want to have long-tailed distribution i.e tail-classes should have a low and different number of samples.