def between(full, start, end):
    """Returns the substring of the given string that occurs between the start
    and end strings."""
    try:
        if not start:
            parse = full
        else:
            parse = full.split(start, 1)[1]
        if end:
            result = parse.split(end, 1)[0]
        else:
            result = parse
        return result
    except:
        return full