Parameter “stratify” from method “train_test_split” (scikit Learn)

Question

I am trying to use train_test_split from package scikit Learn, but I am having trouble with parameter stratify. Hereafter is the code:

Answer 1

For my future self who comes here via Google:

train_test_split is now in model_selection, hence:

from sklearn.model_selection import train_test_split

# given:
# features: xs
# ground truth: ys

x_train, x_test, y_train, y_test = train_test_split(xs, ys,
                                                    test_size=0.33,
                                                    random_state=0,
                                                    stratify=ys)

is the way to use it. Setting the random_state is desirable for reproducibility.