kappa_score.py

from sklearn.metrics import confusion_matrix

def kappa_score(y_true, y_pred):

    cfm = confusion_matrix(y_true, y_pred)
    n_c = len(np.unique(y_true))
    s_0 = np.sum(cfm, axis=0)
    s_1 = np.sum(cfm, axis=1)
    exp = np.outer(s_0, s_1).astype(np.double) / np.sum(s_0) 
    mat = np.ones([n_c, n_c], dtype=np.int)
    mat.flat[::n_c + 1] = 0

    sco = np.sum(mat * cfm) / np.sum(mat * exp)
    
    return 1 - sco