def train_test(df):
    """
    split into train and test set
        train contains Jan 1, 2018 through July 31, 2018
        test contains August 1, 2018 through September 28, 2018
    :param df:
    :return:
    """
    df = df[df['Date'] >= '2018-01-01']

    train = df[df['Date'] < '2018-08-01']

    test = df[df['Date'] >= '2018-08-01']
    test = test[test['Date'] < '2018-09-28']

    return [train, test]