def preprocess(train):
    """
    This method replaces punctuations and newline characters with space character
    given a string. Then it splits all words into a list and returns it.
    
    Parameters:
    train -- The string that will be preprocessed
    
    Returns:
    train -- A list containing words
    """
    
    train = train.replace('\n', ' ')
    
    punctuations = [",", ".", ":", "\"", "'", "/", "\\", "*", "=", "-", "_", ")", "(", "[", "]",
               "{", "}", "%", "+", "!", "@", "#", "$", "^", "&", "+", "|", ";", "<",
               ">", "?", "`", "~", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
    
    for punctuation in punctuations:
        train = train.replace(punctuation, " ")
        
    train = train.split()
    
    return train