"""tuple_basics.py - Python 元组基础示例
一句话总结：元组就是“固定、稳定、不可修改的一组数据”。
包含常见的元组操作示例：创建、访问、切片、拼接、查找、解包、不可变性等。
运行后会打印每个示例的结果，并在代码中注释预期输出。
"""


def main():
    # 1. 创建元组
    nums = (1, 2, 3, 4)
    names = ("alice", "bob", "charlie")
    mixed = (10, "python", True, 3.14)
    empty = ()
    single = (42,)   # 只有一个元素时必须保留逗号

    print("nums ->", nums)
    print("names ->", names)
    print("mixed ->", mixed)
    print("empty ->", empty)
    print("single ->", single)

    # 2. 访问元素
    print("nums[0] ->", nums[0])      # 1
    print("nums[-1] ->", nums[-1])    # 4
    print("names[1] ->", names[1])    # bob

    # 3. 切片
    print("nums[1:3] ->", nums[1:3])    # (2, 3)
    print("names[:2] ->", names[:2])    # ('alice', 'bob')
    print("nums[::-1] ->", nums[::-1])  # 反转，返回新元组

    # 4. 长度和成员判断
    print("len(nums) ->", len(nums))
    print("2 in nums ->", 2 in nums)
    print("5 in nums ->", 5 in nums)

    # 5. 计数和查找
    numbers = (1, 2, 2, 3, 2, 4)
    print("numbers.count(2) ->", numbers.count(2))    # 3
    print("numbers.index(3) ->", numbers.index(3))    # 3

    # 6. 拼接
    print("nums + (5, 6) ->", nums + (5, 6))

    # 7. 元组不可变：不能修改元素
    # 如果取消下面注释，会报错：TypeError
    # nums[0] = 100

    # 8. 多重赋值（解包）
    student = ("Tom", 18, "CS")
    name, age, major = student
    print("unpack ->", name, age, major)

    # 9. 部分解包（*）
    first, *rest, last = (10, 20, 30, 40, 50)
    print("first, *rest, last ->", first, rest, last)

    # 10. 迭代
    for item in names:
        print("loop ->", item)

    # 11. 元组常用于固定数据
    point = (10, 20)
    x, y = point
    print("point = (10, 20), x, y ->", x, y)

    # 12. 与列表区别
    # 列表可以修改，元组不能修改
    list_example = [1, 2, 3]
    tuple_example = (1, 2, 3)

    list_example[0] = 100
    print("list_example after change ->", list_example)
    # tuple_example[0] = 100  # 会报错，元组不可变


if __name__ == '__main__':
    main()