temp = a
a = b
b = temp

a, b = b, a

# 基礎(chǔ)示例
x, y, z = 1, 2, 3
print(x, y, z)  # 輸出: 1 2 3

# 字符串解包
a, b, c = "ABC"
print(a, b, c)  # 輸出: A B C

# 解析CSV行數(shù)據(jù)
record = "Alice,28,Engineer"
name, age, job = record.split(',')
print(f"{name} is {age} years old and works as {job}")
# 輸出: Alice is 28 years old and works as Engineer

# 模擬數(shù)據(jù)庫(kù)查詢
user_data = (101, "Sarah", "sarah@example.com")
user_id, username, email = user_data

# 以下兩種寫法等價(jià)
a, b = (1, 2)
(a, b) = 1, 2

def get_user_info():
    return 101, "Michael", "Data Analyst"

# 直接解包函數(shù)返回值
user_id, name, role = get_user_info()
print(f"ID: {user_id}, Name: {name}, Role: {role}")

# 嵌套元組解包
coordinates = ( (2.3, 4.7), (5.1, 9.2) )
(top_left, top_right) = coordinates
(x1, y1) = top_left
(x2, y2) = top_right

# 一步到位的嵌套解包
((x1, y1), (x2, y2)) = coordinates
print(f"Top Left: ({x1}, {y1}), Top Right: ({x2}, {y2})")

# 錯(cuò)誤示例：元素?cái)?shù)量不匹配
a, b = [1, 2, 3]  # 報(bào)錯(cuò): too many values to unpack

# 基本用法
first, *middle, last = [1, 2, 3, 4, 5]
print(first)   # 1
print(middle)  # [2, 3, 4]
print(last)    # 5

# 星號(hào)可出現(xiàn)在任意位置
*head, x, y = range(5)
print(head)  # [0, 1, 2]
print(x, y)  # 3 4

# 解析帶時(shí)間戳的日志
log_entry = "2023-08-15 INFO User logged in successfully"
timestamp, level, *message = log_entry.split()
print(f"[{timestamp}] [{level}] {' '.join(message)}")
# 輸出: [2023-08-15] [INFO] User logged in successfully

# 單元素序列
a, *b, c = [1]
print(a, b, c)  # 1 [] 報(bào)錯(cuò)! 實(shí)際會(huì)觸發(fā)ValueError

# 兩元素序列
a, *b, c = [1, 2]
print(a, b, c)  # 1 [] 2 → b為空列表

# 列表解包
[x, y, z] = [1, 2, 3]
print(x, y, z)  # 1 2 3

# 元組解包
x, y, z = 1, 2, 3

# 處理坐標(biāo)列表
points = [[1,2], [3,4], [5,6]]
for [x, y] in points:
    print(f"Point at ({x}, {y})")

for x, y in points:  # 更Pythonic的寫法
    print(f"Point at ({x}, {y})")

# 基本用法
names = ["Alice", "Bob", "Charlie"]
scores = [85, 92, 78]

for name, score in zip(names, scores):
    print(f"{name} scored {score}")

# 不推薦的索引方式
for i in range(min(len(names), len(scores))):
    print(f"{names[i]} scored {scores[i]}")

# 三序列并行處理
cities = ["Beijing", "New York", "Tokyo"]
temps = [32, 28, 30]
humidity = [65, 70, 80]

for city, temp, humid in zip(cities, temps, humidity):
    print(f"{city}: {temp}°C, {humid}% humidity")

from itertools import zip_longest

names = ["Alice", "Bob"]
scores = [85, 92, 78, 88]

for name, score in zip_longest(names, scores, fillvalue="N/A"):
    print(f"{name}: {score}")
# 輸出:
# Alice: 85
# Bob: 92
# N/A: 78
# N/A: 88

// Java中的變量交換
int temp = a;
a = b;
b = temp;

a, b = b, a

x = 10
y = 20
x, y = y, x

# 三變量輪換
a, b, c = 1, 2, 3
a, b, c = b, c, a
print(a, b, c)  # 2 3 1

def bubble_sort(arr):
    n = len(arr)
    for i in range(n):
        for j in range(0, n-i-1):
            if arr[j] > arr[j+1]:
                arr[j], arr[j+1] = arr[j+1], arr[j]  # 無(wú)需臨時(shí)變量
    return arr

user = {"name": "Eva", "age": 30, "role": "Designer"}
key1, key2, key3 = user
print(key1, key2, key3)  # name age role

name, age, role = user.values()
print(name, age, role)  # Eva 30 Designer

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

config = {
    "server": "api.example.com",
    "port": 8080,
    "timeout": 30,
    "retries": 3
}

# 僅提取關(guān)鍵配置
main_server, port, *other = config.values()
print(f"Connecting to {main_server}:{port}")

def connect(**settings):
    print(f"Connecting to {settings['host']}:{settings['port']}")

config = {"host": "db.example.com", "port": 5432}
connect(**config)  # 等價(jià)于 connect(host="db...", port=5432)

def calculate(a, b, operation="add"):
    if operation == "add":
        return a + b
    elif operation == "multiply":
        return a * b

# 從配置獲取參數(shù)
params = [5, 10]
operation = {"operation": "multiply"}

# 動(dòng)態(tài)調(diào)用
result = calculate(*params, **operation)
print(result)  # 50

import requests

def api_request(method, url, **params):
    response = requests.request(method, url, params=params)
    response.raise_for_status()
    return response.json()

# 從配置文件讀取請(qǐng)求參數(shù)
request_config = {
    "method": "GET",
    "url": "https://api.example.com/data",
    "params": {"page": 1, "limit": 10}
}

# 動(dòng)態(tài)解包調(diào)用
data = api_request(
    request_config["method"],
    request_config["url"],
    **request_config["params"]
)

# 錯(cuò)誤示例
a, b = [1, 2, 3]  # ValueError: too many values to unpack

# 正確做法
a, b, *c = [1, 2, 3]  # c接收剩余元素

# 錯(cuò)誤示例
(x, y), z = [1, 2, 3]  # TypeError: cannot unpack non-iterable int object

# 正確結(jié)構(gòu)
(x, y), z = [[1, 2], 3]  # 需要匹配嵌套結(jié)構(gòu)

# Python 3.5及更早版本
user = {"name": "Alex", "age": 25}
a, b = user  # 順序不確定!

# 安全做法（所有版本）
a, b = user.keys()  # 顯式獲取鍵列表

gen = (x for x in range(3))
a, b, c = gen  # 正常
print(a, b, c)  # 0 1 2

# 但生成器只能遍歷一次
d, e, f = gen  # ValueError: not enough values to unpack

gen = (x for x in range(3))
data = list(gen)
a, b, c = data

try:
    a, b, c = get_data()
except ValueError as e:
    # 檢查錯(cuò)誤類型
    if "too many" in str(e):
        print("數(shù)據(jù)過(guò)多，請(qǐng)檢查輸入格式")
    elif "not enough" in str(e):
        print("數(shù)據(jù)不足，需要至少3個(gè)字段")
    else:
        raise

data = get_data()
if len(data) != 3:
    handle_error()
else:
    a, b, c = data

# Python 3.10+ 的match-case
def process_point(point):
    match point:
        case (0, 0):
            print("Origin")
        case (x, 0):
            print(f"X-axis at {x}")
        case (0, y):
            print(f"Y-axis at {y}")
        case (x, y):
            print(f"Point at ({x}, {y})")

process_point((3, 4))  # 輸出: Point at (3, 4)

# 傳統(tǒng)方式處理坐標(biāo)
x, y = (3, 4)
if x == 0 and y == 0:
    print("Origin")
elif y == 0:
    print(f"X-axis at {x}")
elif x == 0:
    print(f"Y-axis at {y}")
else:
    print(f"Point at ({x}, {y})")

# 解析嵌套API響應(yīng)
response = {
    "status": "success",
    "data": {
        "user": {
            "id": 101,
            "name": "Taylor"
        },
        "items": [1, 2, 3]
    }
}

# 多層解包
status = response["status"]
user_id = response["data"]["user"]["id"]
user_name = response["data"]["user"]["name"]
first_item = response["data"]["items"][0]

# 一行解包（需Python 3.10+）
match response:
    case {"status": "success", 
          "data": {"user": {"id": uid, "name": uname},
                   "items": [first, *rest]}}:
        print(f"User {uname}({uid}) has item {first}")

# 傳統(tǒng)解包（所有版本）
status = response["status"]
if status == "success":
    data = response["data"]
    user = data["user"]
    items = data["items"]
    uid, uname = user["id"], user["name"]
    first, *rest = items

# config.yaml
server:
  host: "0.0.0.0"
  port: 8000
  ssl: true
database:
  url: "postgres://user:pass@localhost/db"
  timeout: 30
features:
  - "auth"
  - "analytics"
  - "notifications"

import yaml

with open("config.yaml") as f:
    config = yaml.safe_load(f)

# 逐層提取
host = config["server"]["host"]
port = config["server"]["port"]
ssl_enabled = config["server"]["ssl"]
db_url = config["database"]["url"]
# ... 其他參數(shù)

import yaml

with open("config.yaml") as f:
    config = yaml.safe_load(f)

# 服務(wù)器配置
server = config["server"]
(host, port, ssl_enabled) = (server["host"], server["port"], server["ssl"])

# 數(shù)據(jù)庫(kù)配置（更簡(jiǎn)潔的解包）
db_url, timeout = config["database"]["url"], config["database"]["timeout"]

# 功能列表（擴(kuò)展解包）
*enabled_features, = config["features"]  # 等價(jià)于 enabled_features = config["features"]

print(f"Server: {host}:{port}, SSL: {ssl_enabled}")
print(f"Database: {db_url}, Timeout: {timeout}s")
print(f"Features: {', '.join(enabled_features)}")

# 一行解包服務(wù)器配置（Python 3.10+）
(host, port, ssl_enabled) = (config["server"][k] for k in ["host", "port", "ssl"])

# 或使用字典解包
server = config["server"]
host, port, ssl_enabled = [server[k] for k in ("host", "port", "ssl")]

def parse_config(config):
    # 服務(wù)器配置
    server = config["server"]
    db = config["database"]
    
    return {
        "host": server["host"],
        "port": server["port"],
        "ssl": server["ssl"],
        "db_url": db["url"],
        "timeout": db["timeout"],
        "features": config["features"]
    }

# 一次性解包所有配置
app_config = parse_config(config)
host, port, ssl, db_url, timeout, features = (
    app_config[k] for k in ["host", "port", "ssl", "db_url", "timeout", "features"]
)

import timeit

# 交換變量的兩種方式
def swap_with_temp():
    a = 1
    b = 2
    temp = a
    a = b
    b = temp

def swap_with_unpacking():
    a = 1
    b = 2
    a, b = b, a

# 測(cè)試執(zhí)行時(shí)間
temp_time = timeit.timeit(swap_with_temp, number=1000000)
unpack_time = timeit.timeit(swap_with_unpacking, number=1000000)

print(f"臨時(shí)變量: {temp_time:.6f}s")
print(f"解包交換: {unpack_time:.6f}s")

臨時(shí)變量: 0.085231s
解包交換: 0.072846s

data = list(range(1000))

def index_access():
    total = 0
    for i in range(len(data)):
        total += data[i]
    return total

def unpacking():
    total = 0
    for x in data:
        total += x
    return total

print("索引訪問(wèn):", timeit.timeit(index_access, number=1000))
print("解包迭代:", timeit.timeit(unpacking, number=1000))

索引訪問(wèn): 0.182345s
解包迭代: 0.123789s

// JavaScript解構(gòu)
const [first, ...middle, last] = [1,2,3,4]; // 語(yǔ)法錯(cuò)誤！

first, *middle, last = [1,2,3,4]  # 完全合法

// Java實(shí)現(xiàn)多返回值
class Result {
    int a;
    String b;
    // 構(gòu)造函數(shù)等
}

Result getResult() {
    return new Result(1, "text");
}

// 調(diào)用
Result res = getResult();
int a = res.a;
String b = res.b;

# 不推薦：過(guò)度壓縮降低可讀性
a, b, c, d, e = 1, 2, 3, 4, 5

# 推薦：按邏輯分組
x, y = 1, 2
width, height = 100, 200

# 反面示例：三層嵌套難以理解
((a, b), (c, d)), e = nested_data

# 正面示例：分步解包
top_level = nested_data
inner1, inner2, e = top_level
a, b = inner1
c, d = inner2

# 解包數(shù)據(jù)庫(kù)配置
db_host, db_port, db_name = get_db_config()
# ^ host   ^ port  ^ database name

# 不推薦
def get_user():
    return user_id, username, email

# 推薦（使用命名元組或數(shù)據(jù)類）
from collections import namedtuple
User = namedtuple("User", ["id", "name", "email"])

def get_user():
    return User(id=101, name="Alex", email="alex@example.com")

# 調(diào)用時(shí)解包
user_id, username, _ = get_user()  # 忽略email

# 忽略中間值
first, _, last = [1, 2, 3]

# 忽略多個(gè)值
head, *_, tail = range(10)

# 傳統(tǒng)索引方式
timestamps = data[0]
values = data[1]

# 解包思維
timestamps, values = data

match response:
    case {"status": "ok", "data": [x, y, *rest]}:
        process(x, y)

# 在條件中解包
if (data := get_data()) and (a, b := data[0], data[1]):
    print(a, b)

from typing import Tuple

def get_point() -> Tuple[float, float]:
    return (1.5, 2.5)

x: float
y: float
x, y = get_point()  # 類型檢查器能推斷x/y為float