def empty_list(n, content=None):
    """
    Create a list of size n with elements as None or content
    :param n: the size of list
    :param content: the content of all elements
    :return: a size n list with all elements are content
    Example:
        >>> z = empty_list(3)
          z = [None, None, None]
        >>> z = empty_list(4, 'a')
          z = ['a', 'a', 'a', 'a']
    """
    # make a empty list of size n
    return [content for _ in range(0, n)]