To determine the similarity between two instances, we need a distance function. In our example, the Euclidean distance is ideal:
def distance(instance1, instance2):
# just in case, if the instances are lists or tuples:
instance1 = np.array(instance1)
instance2 = np.array(instance2)
return np.linalg.norm(instance1 - instance2)
print(distance([3, 5], [1, 1]))
print(distance(learnset_data[3], learnset_data[44]))
4.472135955
3.41906419946