def get_words(sentence):
    """ (str) -> list
    
    The function takes as input a string representing a sentence.
    It returns a list of the words from the input string.
    
    >>> s = "How wonderful it is that nobody need wait a single moment before starting to improve the world"
    >>> x = get_words(s)
    >>> x == ['How', 'wonderful', 'it', 'is', 'that', 'nobody', 'need', 'wait', 'a', \
    'single', 'moment', 'before', 'starting', 'to', 'improve', 'the', 'world']
    True
    
    >>> s = "Today, I will be staying home all day"
    >>> get_words(s)
    ['Today', 'I', 'will', 'be', 'staying', 'home', 'all', 'day']
    
    >>> s = "Okay; here's a pretty-punctuated sentence: 'Hi, -- how are you'"
    >>> get_words(s)
    ['Okay', 'here', 's', 'a', 'pretty', 'punctuated', 'sentence', 'Hi', 'how', 'are', 'you']
    
    >>> s = ""
    >>> get_words(s)
    []
    """
    # define punctuation symbols that separate phrases                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
    punctuations = [',', '-', '--', ':', ';', '"', "'"]
    
    # replace the punctuation by white spaces
    for punctuation in punctuations:
        sentence = sentence.replace(punctuation, " ")
    
    # split the sentence into words depending on where white spaces are
    words = sentence.split()
    
    # return the list of words from the input sentence
    return words