def count_lines(lst):
    """ (list of str) -> int

    Precondition: each str in lst[:-1] ends in \n.

    Return the number of non-blank, non-empty strings in lst.

    >>> count_lines(['The first line leads off,\n', '\n', '  \n',
    ... With a gap before the next.\n', 'Then the poem ends.\n'])
    3
    """

    total_lines = 0
    blank_lines = 0
    nonblank_lines = 0

    #goes through each element of the list
    for line in lst:
        total_lines += 1
        if line.isalnum() or line.isspace():
            blank_lines += 1
        else:
            nonblank_lines += 1
    print(total_lines, blank_lines, nonblank_lines)
    return nonblank_lines