python 元组、列表、集合、字典有什么区别，分别用在哪里？

# 场景: 待办事项列表、购物车、操作日志
todos = ["写报告", "开会", "发邮件"]
todos.append("加班")          # 动态添加
todos.insert(0, "喝咖啡")     # 插入
todos.remove("开会")          # 删除
for i, task in enumerate(todos):
    print(f"{i}: {task}")

# 场景1: 坐标点、RGB颜色、配置常量
POINT = (116.4, 39.9)         # 经纬度, 不应被修改
RED = (255, 0, 0)

# 场景2: 函数返回多个值
def min_max(nums):
    return (min(nums), max(nums))
lo, hi = min_max([3, 1, 4, 1, 5])

# 场景3: 字典的键 (list 不行, tuple 可以)
locations = {
    (39.9, 116.4): "北京",
    (31.2, 121.5): "上海",
}

# 场景1: 去重
tags = ["python", "java", "python", "go", "java"]
unique_tags = set(tags)       # {'python', 'java', 'go'}

# 场景2: 集合运算
frontend = {"React", "Vue", "CSS"}
backend = {"Python", "Java", "CSS"}
both = frontend & backend       # 交集: {"CSS"}
all_skills = frontend | backend # 并集: 全部
only_front = frontend - backend # 差集: {"React", "Vue"}

# 场景3: 快速成员判断 (O(1) vs list 的 O(n))
valid_ids = {1001, 1002, 1003}
if user_id in valid_ids:        # 极快
    print("已注册")

# 场景1: 对象属性 / 配置
user = {"name": "Alice", "age": 25, "city": "Shanghai"}

# 场景2: 计数 / 频率统计
from collections import Counter
words = ["apple", "banana", "apple", "cherry", "banana", "apple"]
count = dict(Counter(words))    # {"apple": 3, "banana": 2, "cherry": 1}

# 场景3: 缓存 / 查找表
price = {"apple": 5.0, "banana": 3.5, "cherry": 12.0}
total = sum(price[item] for item in cart)

# 场景4: 分组
from collections import defaultdict
groups = defaultdict(list)
for person in people:
    groups[person["department"]].append(person["name"])