import numpy as np

def encode(a):
    result = []
    if a:
        current = a.pop(0)
        counter = 1
        for i in a:
            if i == current:
                counter += 1
            else:
                result.append((counter, current))
                current = i
                counter = 1
        result.append((counter, current))
    return result

X = np.array([1, 2, 2, 3, 3, 1, 1, 5, 5, 2, 3, 3])
num = np_encode(X)