# Get 60% of the dataset as the training set. Put the remaining 40% in temporary variables: x_ and y_.
x_train, x_, y_train, y_ = train_test_split(x, y, test_size=0.40, random_state=1)

# Split the 40% subset above into two: one half for cross validation and the other for the test set
x_cv, x_test, y_cv, y_test = train_test_split(x_, y_, test_size=0.50, random_state=1)

# Delete temporary variables
del x_, y_