def userselect_increment(block):
    """Let user interactively select byte increment."""
    print("Selected block:")
    print('\n    ' + ('\n    '.join(block['lines'])))
    print()

    increment = None
    while increment is None:
        increment = input("Choose store pointer increment (number of bytes): ")
        try:
            increment = int(increment)
        except ValueError:
            increment = None

    block['pointer_increment'] = increment
    return increment
Let user interactively select byte increment.