courses = {"数学", "英语"} 待添加课程："人工智能", "大数据", "物联网"
courses.add("人工智能", "大数据", "物联网")
courses.update(["人工智能", "大数据", "物联网"])
courses.extend(["人工智能", "大数据", "物联网"])
courses.append("人工智能")