跳到主要内容

字典（Dictionary）

字典的基本概念​

  • 字典是**键值对（key-value）**的集合
  • 使用 {} 创建，键与值之间用冒号 : 分隔
student = {
    "name": "Alice",
    "age": 20,
    "is_enrolled": True
}

访问与修改元素​

📌 通过键访问值​

print(student["name"])  # Alice

📌 修改 / 添加键值对​

student["age"] = 21
student["grade"] = "A"

删除元素​

del student["is_enrolled"]
student.pop("age")

遍历字典​

for key in student:
    print(key, "=>", student[key])
for key, value in student.items():
    print(key, value)

常用方法（含示例）​

🔹 .get(key[, default]) — 安全访问键​

print(student.get("name"))          # Alice
print(student.get("address", "N/A"))  # N/A

🔹 .keys() / .values() / .items()​

print(student.keys())    # dict_keys(['name', 'grade'])
print(student.values())  # dict_values(['Alice', 'A'])
print(student.items())   # dict_items([('name', 'Alice'), ('grade', 'A')])

🔹 .update() — 批量更新键值对​

student.update({"age": 22, "city": "Brisbane"})

🔹 .clear() — 清空字典​

student.clear()
print(student)  # {}

嵌套字典（进阶）​

students = {
    "001": {"name": "Alice", "age": 20},
    "002": {"name": "Bob", "age": 21}
}
print(students["001"]["name"])  # Alice

📚 总结​

操作示例
创建字典{"a": 1, "b": 2}
访问键dict["a"] or dict.get("a")
添加/更新dict["c"] = 3 or .update({...})
删除键del dict["a"], dict.pop("a")
遍历for k, v in dict.items()
嵌套结构dict["key1"]["key2"]