def append(x,v):
    """
    >>> append(mylist,20)
    >>> mylist
    [1, 2, 3, 20]
    """
    x.append(v)

def prepend(x,v):
    """
    >>> prepend(mylist,30)
    >>> mylist
    [30, 1, 2, 3]
    """
    x.insert(0,v)

if __name__ == "__main__":
    import doctest
    # I'd like each test to see the same input, but I can't.
    doctest.testmod(extraglobs={'mylist': [1,2,3] })