# 基本變量插入
name = "Alice"
age = 25
print(f"姓名: {name}, 年齡: {age}")  # 姓名: Alice, 年齡: 25

# 表達(dá)式計算
a, b = 5, 3
print(f"{a} +  = {a + b}")  # 5 + 3 = 8
print(f"{a} 的平方是 {a ** 2}")  # 5 的平方是 25

# 方法調(diào)用
text = "hello world"
print(f"大寫: {text.upper()}")  # 大寫: HELLO WORLD

# 數(shù)字格式化
pi = 3.1415926535
print(f"π ≈ {pi:.2f}")        # π ≈ 3.14
print(f"π ≈ {pi:8.3f}")       # π ≈    3.142
print(f"整數(shù): {age:04d}")      # 整數(shù): 0025

# 百分比
score = 0.856
print(f"正確率: {score:.1%}")  # 正確率: 85.6%

# 科學(xué)計數(shù)法
large_num = 123456789
print(f"科學(xué)計數(shù): {large_num:.2e}")  # 科學(xué)計數(shù): 1.23e+08

# 字典和對象訪問
person = {"name": "Bob", "age": 30}
print(f"姓名: {person['name']}, 年齡: {person['age']}")

class User:
    def __init__(self, name, level):
        self.name = name
        self.level = level

user = User("Charlie", 5)
print(f"用戶: {user.name}, 等級: {user.level}")

# 嵌套 f-string
width = 10
precision = 4
value = 12.34567
print(f"結(jié)果: {value:{width}.{precision}}")  # 結(jié)果:     12.35

# 多行 f-string
message = f"""
用戶信息:
  姓名: {name}
  年齡: {age}
  分?jǐn)?shù): {score:.1%}
"""
print(message)

# 條件表達(dá)式
is_admin = True
print(f"權(quán)限: {'管理員' if is_admin else '普通用戶'}")  # 權(quán)限: 管理員

# 普通字符串中的轉(zhuǎn)義問題
print("C:\new\folder")  
# 輸出:
# C:
# ew
# older

# 使用原始字符串
print(r"C:\new\folder")  # C:\new\folder

# 正則表達(dá)式中的使用
import re
pattern = r"\d{3}-\d{4}"  # 匹配電話號碼
text = "電話: 123-4567"
match = re.search(pattern, text)
print(match.group() if match else "未匹配")  # 123-4567

# 文件路徑處理
import os

# 不使用原始字符串（容易出錯）
path1 = "C:\\Users\\Alice\\Documents\\file.txt"
# 使用原始字符串（更清晰）
path2 = r"C:\Users\Alice\Documents\file.txt"

print(f"路徑1: {path1}")
print(f"路徑2: {path2}")

# Windows 路徑處理
folder = r"C:\Program Files\MyApp"
filename = "config.ini"
full_path = os.path.join(folder, filename)
print(f"完整路徑: {full_path}")

# 正則表達(dá)式模式
email_pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
url_pattern = r"https?://(?:[-\w.]|(?:%[\da-fA-F]{2}))+"

# 原始字符串的局限性
# print(r"末尾不能有單個反斜杠\")  # 語法錯誤
print(r"可以有兩個反斜杠\\")     # 可以有兩個反斜杠\\
print(r"但這樣沒問題\ ")         # 但這樣沒問題\ 

# 混合使用技巧
base_path = r"C:\Users\Alice"
file_name = "document.txt"
full_path = fr"{base_path}\{file_name}"  # 原始格式化字符串
print(full_path)  # C:\Users\Alice\document.txt

# 創(chuàng)建字節(jié)字符串
byte_data = b"hello world"
print(byte_data)           # b'hello world'
print(type(byte_data))     # <class 'bytes'>

# 字節(jié)與整數(shù)的關(guān)系
for byte in b"ABC":
    print(byte, chr(byte))
# 65 A
# 66 B  
# 67 C

# 只能包含 ASCII 字符
# b"中文"  # 語法錯誤，需要使用編碼
chinese_bytes = "中文".encode('utf-8')
print(chinese_bytes)  # b'\xe4\xb8\xad\xe6\x96\x87'

# 文件讀寫
# 寫入二進(jìn)制數(shù)據(jù)
with open('binary_file.bin', 'wb') as f:
    f.write(b'\x00\x01\x02\x03\x04')

# 讀取二進(jìn)制數(shù)據(jù)
with open('binary_file.bin', 'rb') as f:
    data = f.read()
    print(f"讀取的數(shù)據(jù): {data}")  # b'\x00\x01\x02\x03\x04'

# 網(wǎng)絡(luò)編程
import socket

# 模擬網(wǎng)絡(luò)數(shù)據(jù)包
packet_header = b"PKT"
packet_data = b"payload data"
full_packet = packet_header + b"\x00" + packet_data
print(f"完整數(shù)據(jù)包: {full_packet}")

# 編碼解碼
text = "Hello 世界"
encoded = text.encode('utf-8')  # 字符串轉(zhuǎn)字節(jié)
decoded = encoded.decode('utf-8')  # 字節(jié)轉(zhuǎn)字符串
print(f"編碼后: {encoded}")
print(f"解碼后: {decoded}")

# Python 3 中 u 前綴是可選的
unicode_str1 = u"Hello 世界"
unicode_str2 = "Hello 世界"  # 效果相同

print(unicode_str1)  # Hello 世界
print(unicode_str2)  # Hello 世界
print(unicode_str1 == unicode_str2)  # True

# 處理特殊 Unicode 字符
emoji_str = u"Python is fun! ????"
print(emoji_str)  # Python is fun! ????

# Unicode 轉(zhuǎn)義序列
unicode_escape = u"\u4e2d\u6587"  # 中文
print(unicode_escape)  # 中文

# 處理包含反斜杠的格式化字符串
username = "Alice"
file_path = fr"C:\Users\{username}\Documents\file.txt"
print(file_path)  # C:\Users\Alice\Documents\file.txt

# 正則表達(dá)式模板
base_pattern = r"\d{3}"
full_pattern = fr"{base_pattern}-\d{4}"
text = "電話號碼: 123-4567"
match = re.search(full_pattern, text)
print(match.group() if match else "未匹配")  # 123-4567

# 字節(jié)格式化 (Python 3.5+)
name = b"Alice"
age = 25
# 注意：字節(jié)字符串的 f-string 有限制
message = b"Name: " + name + b", Age: " + str(age).encode()
print(message)  # b'Name: Alice, Age: 25'

def create_config_template():
    """創(chuàng)建配置文件模板"""
    
    database_host = "localhost"
    database_port = 5432
    log_path = r"C:\App\Logs"
    
    config_template = f"""
[database]
host = {database_host}
port = {database_port}
username = admin
password = secret

[logging]
path = {log_path}
level = INFO
"""
    return config_template

print(create_config_template())

class PathBuilder:
    """路徑構(gòu)建工具類"""
    
    def __init__(self, base_path):
        self.base_path = base_path
    
    def file_path(self, filename):
        return fr"{self.base_path}\{filename}"
    
    def subfolder_path(self, folder_name, filename):
        return fr"{self.base_path}\{folder_name}\{filename}"

# 使用示例
builder = PathBuilder(r"C:\MyApp")
print(builder.file_path("config.ini"))        # C:\MyApp\config.ini
print(builder.subfolder_path("logs", "app.log"))  # C:\MyApp\logs\app.log

def serialize_data(data):
    """序列化數(shù)據(jù)為字節(jié)格式"""
    
    header = b"DATA"
    version = b"\x01\x00"
    
    # 將數(shù)據(jù)轉(zhuǎn)換為字節(jié)
    if isinstance(data, str):
        content = data.encode('utf-8')
    elif isinstance(data, int):
        content = str(data).encode('utf-8')
    else:
        content = bytes(data)
    
    # 構(gòu)建完整數(shù)據(jù)包
    packet = header + version + len(content).to_bytes(4, 'big') + content
    return packet

def deserialize_data(packet):
    """從字節(jié)數(shù)據(jù)反序列化"""
    if packet[:4] != b"DATA":
        raise ValueError("無效的數(shù)據(jù)格式")
    
    content_length = int.from_bytes(packet[6:10], 'big')
    content = packet[10:10+content_length]
    
    try:
        return content.decode('utf-8')
    except UnicodeDecodeError:
        return content

# 測試
original_data = "Hello, 世界!"
serialized = serialize_data(original_data)
print(f"序列化: {serialized}")
deserialized = deserialize_data(serialized)
print(f"反序列化: {deserialized}")

import timeit

def performance_comparison():
    """不同字符串格式化方法的性能比較"""
    
    name = "Alice"
    age = 25
    score = 95.5
    
    # 測試不同的格式化方法
    tests = {
        "f-string": 'f"姓名: {name}, 年齡: {age}, 分?jǐn)?shù): {score:.1f}"',
        "format()": '"姓名: {}, 年齡: {}, 分?jǐn)?shù): {:.1f}".format(name, age, score)',
        "% 格式化": '"姓名: %s, 年齡: %d, 分?jǐn)?shù): %.1f" % (name, age, score)'
    }
    
    print("性能比較 (執(zhí)行100,000次):")
    for name, code in tests.items():
        time_taken = timeit.timeit(code, globals=globals(), number=100000)
        print(f"  {name}: {time_taken:.4f} 秒")

performance_comparison()

def string_prefix_guidelines():
    """字符串前綴選擇指南"""
    
    guidelines = {
        "f-string": [
            "需要插入變量或表達(dá)式時",
            "性能要求高的場景",
            "代碼可讀性重要的地方"
        ],
        "r-string": [
            "正則表達(dá)式模式",
            "Windows 文件路徑",
            "包含大量反斜杠的字符串"
        ],
        "b-string": [
            "處理二進(jìn)制數(shù)據(jù)",
            "網(wǎng)絡(luò)通信",
            "文件 I/O 操作"
        ],
        "組合前綴": [
            "fr: 需要原始字符串和變量插值",
            "根據(jù)實(shí)際需求靈活組合"
        ]
    }
    
    return guidelines

# 打印指南
for prefix, uses in string_prefix_guidelines().items():
    print(f"{prefix}:")
    for use_case in uses:
        print(f"  - {use_case}")

def safe_string_operations():
    """安全的字符串操作"""
    
    # f-string 中的錯誤處理
    try:
        # 可能引發(fā)異常的表達(dá)
        result = f"計算: {1/0}"
    except ZeroDivisionError:
        result = "計算: 錯誤"
    print(result)
    
    # 字節(jié)字符串的編碼處理
    text = "特殊字符: ?, é, 中文"
    try:
        # 嘗試 ASCII 編碼（會失?。?
        ascii_bytes = text.encode('ascii')
    except UnicodeEncodeError:
        # 回退到 UTF-8
        utf8_bytes = text.encode('utf-8', errors='replace')
        print(f"UTF-8 編碼: {utf8_bytes}")
    
    # 路徑安全處理
    import os
    user_input = "some_file.txt"
    # 不安全的方式
    # unsafe_path = fr"C:\Program Files\{user_input}"
    # 安全的方式
    safe_path = os.path.join(r"C:\Program Files", user_input)
    print(f"安全路徑: {safe_path}")

safe_string_operations()