def sequence_minus(seq1, seq2):
    """Calculate difference of two sequences.

    Result contains the elements from first sequence that are not
    present in second sequence, in original order. Works even
    if sequence elements are not hashable.
    """
    result = list(seq1)
    for item in seq2:
        try:
            result.remove(item)
        except ValueError:
            pass
    return result