Python容器从列表、元组、集合到字典，重点掌握dict示例详解

# 直接创建
numbers = [1, 2, 3, 4, 5]

# 允许重复元素
names = ["张三", "李四", "张三"]

# 不同类型的数据可以混合存储
data = [1, "Python", True, 3.14]

# 创建空列表
items = []

# 使用 list() 转换
values = list(range(5))

print(values)  # [0, 1, 2, 3, 4]

fruits = ["苹果", "香蕉", "橙子"]

# 添加元素
fruits.append("葡萄")

# 在指定位置插入元素
fruits.insert(1, "西瓜")

# 删除指定元素，删除第一个匹配项
fruits.remove("香蕉")

# 根据索引删除并返回元素
item = fruits.pop(0)

# 修改元素
fruits[0] = "芒果"

# 获取长度
print(len(fruits))

# 判断元素是否存在
print("橙子" in fruits)

numbers = [10, 20, 30, 40, 50, 60]

print(numbers[1:4])   # [20, 30, 40]
print(numbers[:3])    # [10, 20, 30]
print(numbers[3:])    # [40, 50, 60]
print(numbers[::2])   # [10, 30, 50]
print(numbers[::-1])  # 倒序列表

list[start:stop:step]

# 生成 0 到 9 的平方
squares = [x ** 2 for x in range(10)]

# 筛选偶数
even_numbers = [x for x in range(20) if x % 2 == 0]

# 对字符串进行转换
names = ["alice", "bob", "tom"]
upper_names = [name.upper() for name in names]

print(even_numbers)
print(upper_names)

point = (10, 20)
user = ("张三", 25, "北京")

# 单元素元组必须带逗号
single = (10,)

# 不带括号也可以创建元组
coordinates = 10, 20

# 创建空元组
empty = ()

a = (10)
b = (10,)

print(type(a))  # <class 'int'>
print(type(b))  # <class 'tuple'>

person = ("张三", 25, "北京")

print(person[0])
print(person[1:])
print(len(person))

# 解包
name, age, city = person

# 扩展解包
first, *middle, last = (1, 2, 3, 4, 5)

print(name, age, city)
print(middle)  # [2, 3, 4]

data = ([1, 2], 3)
data[0].append(4)

print(data)  # ([1, 2, 4], 3)

numbers = {1, 2, 3, 4}

# 自动去重
values = {1, 2, 2, 3, 3}

# 创建空集合
empty_set = set()

print(values)  # {1, 2, 3}

numbers = {1, 2, 3}

numbers.add(4)
numbers.update([5, 6, 7])

numbers.remove(2)   # 元素不存在时会抛出 KeyError
numbers.discard(10) # 元素不存在时不会报错

item = numbers.pop()  # 移除并返回一个元素

a = {1, 2, 3, 4}
b = {3, 4, 5, 6}

# 并集：属于任意一个集合
print(a | b)

# 交集：同时属于两个集合
print(a & b)

# 差集：属于 a，但不属于 b
print(a - b)

# 对称差集：只属于其中一个集合
print(a ^ b)

user = {
    "name": "张三",
    "age": 25,
    "city": "北京"
}

print(user["name"])  # 张三
print(user["age"])   # 25

user = {
    "name": "张三",
    "age": 25,
    "is_active": True
}

user = dict(name="张三", age=25, city="北京")
print(user)

data = [
    ("name", "张三"),
    ("age", 25),
    ("city", "北京")
]

user = dict(data)
print(user)

keys = ["name", "age", "city"]
user = dict.fromkeys(keys, None)

print(user)
# {'name': None, 'age': None, 'city': None}

data = dict.fromkeys(["a", "b"], [])

data["a"].append(1)

print(data)
# {'a': [1], 'b': [1]}

data = {key: [] for key in ["a", "b"]}

user = {"name": "张三", "age": 25}

# 新增键值对
user["city"] = "北京"

# 修改已有值
user["age"] = 26

print(user)

user = {"name": "张三", "age": 25}

print(user["name"])

# 键不存在时返回默认值
print(user.get("email", "未填写"))

user = {"name": "张三"}

print(user.get("age"))  # None
print(user.get("age", 0))  # 0

# user["age"] 会抛出 KeyError

data = {"name": None}

print("name" in data)  # True
print("age" in data)   # False

user = {
    "name": "张三",
    "age": 25,
    "city": "北京"
}

# 删除指定键
del user["age"]

# 删除并返回值
city = user.pop("city")

# 不存在时返回默认值
email = user.pop("email", None)

# 删除并返回最后插入的键值对
key, value = user.popitem()

# 清空字典
user.clear()

user = {
    "name": "张三",
    "age": 25
}

user.update({
    "age": 26,
    "city": "北京"
})

print(user)
# {'name': '张三', 'age': 26, 'city': '北京'}

user = {"name": "张三"}

age = user.setdefault("age", 18)

print(age)   # 18
print(user)  # {'name': '张三', 'age': 18}

user = {
    "name": "张三",
    "age": 25,
    "city": "北京"
}

for key in user:
    print(key)

for key in user.keys():
    print(key)

for value in user.values():
    print(value)

for key, value in user.items():
    print(f"{key}: {value}")

inventory = {
    "苹果": 100,
    "香蕉": 80,
    "橙子": 60
}

for product, count in inventory.items():
    print(f"{product} 剩余库存：{count}")

{key表达式: value表达式 for item in iterable}

squares = {
    x: x ** 2
    for x in range(1, 6)
}

print(squares)
# {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}

scores = {
    "张三": 85,
    "李四": 58,
    "王五": 92,
    "赵六": 65
}

passed = {
    name: score
    for name, score in scores.items()
    if score >= 60
}

print(passed)

prices = {
    "apple": 10,
    "banana": 5,
    "orange": 8
}

discount_prices = {
    name: price * 0.8
    for name, price in prices.items()
}

print(discount_prices)

default_config = {
    "host": "127.0.0.1",
    "port": 8000,
    "debug": False
}

user_config = {
    "port": 9000,
    "debug": True
}

default_config.update(user_config)

print(default_config)

default_config = {
    "host": "127.0.0.1",
    "port": 8000
}

user_config = {
    "port": 9000,
    "debug": True
}

config = default_config | user_config

print(config)

config = {
    **default_config,
    **user_config
}

config = {
    **default_config,
    **user_config,
    "version": "1.0"
}

scores = {
    "王五": 92,
    "张三": 85,
    "李四": 78
}

result = dict(sorted(scores.items()))

print(result)

scores = {
    "王五": 92,
    "张三": 85,
    "李四": 78
}

result = dict(
    sorted(
        scores.items(),
        key=lambda item: item[1]
    )
)

print(result)

result = dict(
    sorted(
        scores.items(),
        key=lambda item: item[1],
        reverse=True
    )
)

users = {
    1001: {
        "name": "张三",
        "age": 25,
        "address": {
            "province": "河南",
            "city": "安阳"
        }
    },
    1002: {
        "name": "李四",
        "age": 30,
        "address": {
            "province": "北京",
            "city": "北京"
        }
    }
}

print(users[1001]["name"])
print(users[1001]["address"]["city"])

user = users.get(1001, {})
address = user.get("address", {})
city = address.get("city")

print(city)

original = {
    "name": "张三",
    "scores": [80, 90, 95]
}

copied = original.copy()

copied["name"] = "李四"
copied["scores"].append(100)

print(original)
print(copied)

import copy

original = {
    "name": "张三",
    "scores": [80, 90, 95]
}

copied = copy.deepcopy(original)

copied["scores"].append(100)

print(original["scores"])  # [80, 90, 95]
print(copied["scores"])    # [80, 90, 95, 100]

text = "python is easy python is powerful"

word_count = {}

for word in text.split():
    word_count[word] = word_count.get(word, 0) + 1

print(word_count)

word_count[word] = word_count.get(word, 0) + 1

from collections import Counter

text = "python is easy python is powerful"

word_count = Counter(text.split())

print(word_count)
print(word_count.most_common(2))

from collections import defaultdict

students = [
    ("张三", "一班"),
    ("李四", "二班"),
    ("王五", "一班"),
    ("赵六", "二班")
]

groups = defaultdict(list)

for name, class_name in students:
    groups[class_name].append(name)

print(dict(groups))

groups = {}

for name, class_name in students:
    groups.setdefault(class_name, []).append(name)

cache = {}

def square(n):
    if n not in cache:
        print("执行计算")
        cache[n] = n * n

    return cache[n]


print(square(5))  # 执行计算，然后输出 25
print(square(5))  # 直接返回缓存结果 25

from fastapi import FastAPI

app = FastAPI()


@app.get("/user/{user_id}")
def get_user(user_id: int):
    return {
        "code": 200,
        "message": "success",
        "data": {
            "user_id": user_id,
            "name": "张三",
            "active": True
        }
    }

user = {
    "name": "张三",
    "age": 25
}

print(user["name"])

user_ids = [1001, 1002, 1003, 1004]

print(1003 in user_ids)

user_map = {
    1001: "张三",
    1002: "李四",
    1003: "王五"
}

print(1003 in user_map)

data = {
    [1, 2, 3]: "value"
}

data = {
    (1, 2, 3): "value"
}

data = {
    (1, [2, 3]): "value"
}