what it means X is not defined and how solve it?


In [8]: nb GaussianNB() errs-[] nsplits-1000 for split in range(nsplits): xtrain, xtest, ytrain, ytest – train_test_split (X, Y) gnb.fit(xtrain, ytrain) YP-gnb.predict (xtest) errs.append(1-accuracy_score (ytest, YP)) print (np.mean(errs), np.std(errs) ) NameError Traceback (most recent call last) in 5 6 7 NameError: name 'X' is not defined