Python 進階探索

# 提示使用者輸入攝氏溫度
celsius_str = input("請輸入攝氏溫度：")

# 將字串轉換為浮點數
celsius_float = float(celsius_str)

# 計算華氏溫度
fahrenheit = (celsius_float * 9/5) + 32

# 使用 f-string 格式化輸出
print(f"{celsius_float}°C 等於 {fahrenheit:.1f}°F")
                                

message = "我是全域變數"

def greet():
    message = "我是區域變數"
    print(f"在函式內部: {message}")

if __name__ == "__main__":
    greet()
    print(f"在函式外部: {message}")

# 預期輸出:
# 在函式內部: 我是區域變數
# 在函式外部: 我是全域變數
                                

def generate_greeting():
    CURRENT_YEAR = 2024

    name = input("請問您的名字是？ ")
    birth_year_str = input("請問您的出生年份是？ ")

    # 將年份字串轉為整數
    birth_year = int(birth_year_str)

    # 計算年齡
    age = CURRENT_YEAR - birth_year

    # 使用 f-string 產生問候語
    greeting = f"你好, {name}！你今年大約 {age} 歲。"
    print(greeting)

if __name__ == "__main__":
    generate_greeting()
                                

def get_age():
    while True:
        try:
            age_str = input("請輸入您的年齡: ")
            age = int(age_str)
            if age > 0:
                return age
            else:
                print("錯誤：年齡必須是正數。")
        except ValueError:
            print("錯誤：請輸入一個有效的整數。")

if __name__ == "__main__":
    user_age = get_age()
    print(f"您的年齡是: {user_age}")
                                

def get_value(data_dict, key, default_value="N/A"):
    try:
        value = data_dict[key]
    except KeyError:
        print(f"找不到鍵 '{key}'，回傳預設值。")
        return default_value
    else:
        print(f"成功找到鍵 '{key}'。")
        return value

if __name__ == "__main__":
    student_scores = {"Alice": 95, "Bob": 88}
    
    # 成功案例
    score1 = get_value(student_scores, "Alice")
    print(f"Alice 的分數是: {score1}")

    print("-" * 20)

    # 失敗案例
    score2 = get_value(student_scores, "Charlie")
    print(f"Charlie 的分數是: {score2}")
                                

import unittest

# --- 要被測試的函式 ---
def calculate_area(width, height):
    """計算矩形面積。如果任一邊長小於等於0，面積為0。"""
    if width <= 0 or height <= 0:
        return 0
    return width * height

# --- 測試案例 ---
class TestCalculateArea(unittest.TestCase):

    def test_positive_inputs(self):
        """測試正數輸入"""
        self.assertEqual(calculate_area(10, 5), 50)
        self.assertEqual(calculate_area(7, 3), 21)

    def test_zero_or_negative_inputs(self):
        """測試零或負數輸入"""
        self.assertEqual(calculate_area(10, 0), 0)
        self.assertEqual(calculate_area(0, 5), 0)
        self.assertEqual(calculate_area(-4, 5), 0)
        self.assertEqual(calculate_area(10, -2), 0)

if __name__ == '__main__':
    # 這會執行此檔案中所有的測試案例
    unittest.main(argv=['first-arg-is-ignored'], exit=False)
                                

note_content = """這是第一行筆記。
這是第二行。
檔案處理是Python的重要技能。
"""
file_name = "note.txt"

try:
    # 寫入檔案
    with open(file_name, 'w', encoding='utf-8') as f:
        f.write(note_content)
    print(f"成功將筆記寫入 {file_name}")

    # 讀取檔案並印出
    with open(file_name, 'r', encoding='utf-8') as f:
        read_content = f.read()
        print("\n讀取的筆記內容：")
        print(read_content)

except IOError as e:
    print(f"處理檔案時發生錯誤: {e}")
                                

import json

user_config = {
    "username": "test_user",
    "theme": "dark",
    "notifications": {
        "email": True,
        "sms": False
    }
}
config_file = "config.json"

# 儲存設定到 JSON 檔案
with open(config_file, 'w', encoding='utf-8') as f:
    json.dump(user_config, f, indent=4)
print(f"設定已儲存至 {config_file}")

# 從 JSON 檔案載入設定
with open(config_file, 'r', encoding='utf-8') as f:
    loaded_config = json.load(f)
print("\n成功載入設定。")

# 印出特定設定
print(f"使用者主題設定為: {loaded_config['theme']}")
                                

import csv

# 準備資料
header = ['ProductID', 'ProductName', 'Price']
sales_data = [
    ['P001', 'Laptop', 1200],
    ['P002', 'Mouse', 25],
    ['P003', 'Keyboard', 75]
]
csv_file = "sales.csv"

# 寫入 CSV 檔案
with open(csv_file, 'w', newline='', encoding='utf-8') as f:
    writer = csv.writer(f)
    
    # 寫入標頭
    writer.writerow(header)
    
    # 寫入資料
    writer.writerows(sales_data)

print(f"銷售紀錄已成功寫入 {csv_file}")

# (選做) 讀取並驗證內容
with open(csv_file, 'r', newline='', encoding='utf-8') as f:
    reader = csv.reader(f)
    print("\nCSV 檔案內容：")
    for row in reader:
        print(row)
                                

import tkinter as tk

# 1. 建立主視窗
window = tk.Tk()

# 2. 設定視窗標題
window.title("我的第一個GUI")

# 3. 建立 Label 元件
label = tk.Label(window, text="歡迎來到Tkinter!", font=("Arial", 16), padx=20, pady=20)
label.pack() # 將元件放到視窗中

# 4. 啟動事件迴圈
window.mainloop()
                                

import streamlit as st

# 設定網頁標題
st.title("數字平方計算機")

# 建立一個滑桿
number = st.slider("請選擇一個數字", 1, 100, 25)

# 計算平方
squared_number = number * number

# 顯示結果
st.write(f"你選擇的數字是: {number}")
st.write(f"{number} 的平方是: {squared_number}")
                                

import tkinter as tk

# 1. 建立主視窗
window = tk.Tk()

# 2. 設定視窗標題
window.title("我的第一個GUI")

# 3. 建立 Label 元件
label = tk.Label(window, text="歡迎來到Tkinter!", font=("Arial", 16), padx=20, pady=20)
label.pack() # 將元件放到視窗中

# 4. 啟動事件迴圈
window.mainloop()
                                

import streamlit as st

# 設定網頁標題
st.title("數字平方計算機")

# 建立一個滑桿
number = st.slider("請選擇一個數字", 1, 100, 25)

# 計算平方
squared_number = number * number

# 顯示結果
st.write(f"你選擇的數字是: {number}")
st.write(f"{number} 的平方是: {squared_number}")
                                

import tkinter as tk
import webbrowser

def open_website():
    """在預設瀏覽器中開啟指定的網址"""
    url = "https://www.pythonanywhere.com"
    webbrowser.open(url)
    print(f"正在開啟: {url}")

# 建立主視窗
window = tk.Tk()
window.title("網頁開啟器")

# 建立說明文字
label = tk.Label(window, text="點擊按鈕以了解 Web-based App 部署平台。", padx=20, pady=10)
label.pack()

# 建立按鈕
button = tk.Button(
    window,
    text="前往 PythonAnywhere",
    command=open_website,
    font=("Arial", 12),
    bg="lightblue"
)
button.pack(pady=10)

# 啟動事件迴圈
window.mainloop()
                                

class BankAccount:
    def __init__(self, account_holder, balance=0):
        self.account_holder = account_holder
        self._balance = balance  # 使用底線表示為內部屬性

    def deposit(self, amount):
        if amount > 0:
            self._balance += amount
            print(f"存款 {amount} 元成功。")
        else:
            print("存款金額必須為正數。")

    def withdraw(self, amount):
        if 0 < amount <= self._balance:
            self._balance -= amount
            print(f"提款 {amount} 元成功。")
        else:
            print("提款失敗：金額無效或餘額不足。")

    def get_balance(self):
        return self._balance

if __name__ == '__main__':
    my_account = BankAccount("John Doe", 1000)
    print(f"{my_account.account_holder} 的帳戶餘額: {my_account.get_balance()}")
    my_account.deposit(500)
    my_account.withdraw(200)
    my_account.withdraw(1500)
    print(f"最終餘額: {my_account.get_balance()}")
                                

class Vehicle:
    def __init__(self, brand, year):
        self.brand = brand
        self.year = year

    def display_info(self):
        print(f"品牌: {self.brand}, 年份: {self.year}")

class Car(Vehicle):
    def __init__(self, brand, year, doors):
        super().__init__(brand, year)
        self.doors = doors
    
    def display_info(self):
        super().display_info()
        print(f"車門數: {self.doors}")

class Motorcycle(Vehicle):
    def __init__(self, brand, year, cc):
        super().__init__(brand, year)
        self.cc = cc

    def display_info(self):
        super().display_info()
        print(f"排氣量: {self.cc}cc")

if __name__ == '__main__':
    my_car = Car("Toyota", 2022, 4)
    my_moto = Motorcycle("Yamaha", 2023, 300)

    print("--- 汽車資訊 ---")
    my_car.display_info()
    
    print("\n--- 機車資訊 ---")
    my_moto.display_info()
                                

class Vector2D:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __str__(self):
        """回傳向量的字串表示"""
        return f"({self.x}, {self.y})"

    def __add__(self, other):
        """定義向量的加法運算"""
        if isinstance(other, Vector2D):
            new_x = self.x + other.x
            new_y = self.y + other.y
            return Vector2D(new_x, new_y)
        else:
            # 處理型別不匹配的情況
            return NotImplemented

if __name__ == '__main__':
    v1 = Vector2D(1, 2)
    v2 = Vector2D(3, 4)

    # 測試 __str__
    print(f"向量 v1 是 {v1}")
    print(f"向量 v2 是 {v2}")

    # 測試 __add__
    v3 = v1 + v2
    print(f"v1 + v2 的結果是 {v3}")
                                

import re

def is_valid_email(email):
    # ^               - 字串開頭
    # [\w.-]+         - 匹配使用者名稱 (字母,數字,底線,點,連字號) 至少一次
    # @               - 匹配 @ 符號
    # [a-zA-Z0-9-]+   - 匹配網域名稱 (字母,數字,連字號) 至少一次
    # \.              - 匹配點 .
    # [a-zA-Z]{2,}    - 匹配頂級網域 (字母) 至少兩次
    # $               - 字串結尾
    pattern = r"^[\w.-]+@[a-zA-Z0-9-]+\.[a-zA-Z]{2,}$"
    if re.match(pattern, email):
        return True
    else:
        return False

if __name__ == '__main__':
    print(f"test@example.com -> {is_valid_email('test@example.com')}")
    print(f"invalid-email -> {is_valid_email('invalid-email')}")
    print(f"test@domain -> {is_valid_email('test@domain')}")
    print(f"my.name_123@sub-domain.co.uk -> {is_valid_email('my.name_123@sub-domain.co.uk')}")
                                

import re

text_with_urls = """
我們的官網是 https://www.example.com，請參考。
舊的網址 http://old.example.org/index.html 也還能用。
但不要連到 ftp://internal.server。
文件在 https://docs.python.org/3/library/re.html。
"""

# https?       - 匹配 http 或 https
# ://          - 匹配 ://
# [\w./-]+     - 匹配網址路徑中的合法字元
pattern = r"https?://[\w./-]+"

urls = re.findall(pattern, text_with_urls)

print("提取到的所有網址:")
for url in urls:
    print(url)
                                

import re

def clean_phone_number(phone_str):
    # \D - 匹配任何非數字字元
    cleaned_number = re.sub(r"\D", "", phone_str)
    return cleaned_number

if __name__ == '__main__':
    numbers_to_clean = [
        "(02)-1234-5678",
        "0912 345 678",
        "04-2233 4455",
        "+886-987-654-321"
    ]

    print("清理後的電話號碼:")
    for num in numbers_to_clean:
        cleaned = clean_phone_number(num)
        print(f"'{num}' -> '{cleaned}'")
                                

# --- 檔案 1: my_calculator.py ---
def add(x, y):
    """回傳兩數相加的結果"""
    return x + y

def multiply(x, y):
    """回傳兩數相乘的結果"""
    return x * y

# --- 檔案 2: main.py ---
# 從 my_calculator 模組匯入函式
from my_calculator import add, multiply

if __name__ == "__main__":
    num1 = 15
    num2 = 5

    sum_result = add(num1, num2)
    product_result = multiply(num1, num2)

    print(f"{num1} + {num2} = {sum_result}")
    print(f"{num1} * {num2} = {product_result}")
                

# 1. 安裝套件
pip install requests matplotlib

# 2. 匯出依賴關係
pip freeze > requirements.txt

# 3. 從檔案安裝套件
pip install -r requirements.txt
                

# 1. 建立並進入資料夾
mkdir data_analyzer
cd data_analyzer

# 2. 建立虛擬環境
python -m venv .venv

# 3. 啟動虛擬環境
# Windows:
.venv\Scripts\activate
# macOS / Linux:
source .venv/bin/activate

# 4. 安裝 pandas
pip install pandas
                

if __name__ == "__main__":
    # 全域(此腳本內)作用域變數
    total_sum = 0
    invalid_entries = []

    user_input = input("請輸入一串由逗號分隔的數字: ")
    number_strings = user_input.split(',')

    for num_str in number_strings:
        # 迴圈內的區域作用域變數
        item = num_str.strip()
        try:
            # 型別轉換 (casting)
            number = float(item)
            total_sum += number
        except ValueError:
            # 異常捕捉
            invalid_entries.append(item)
    
    # 使用 f-string 格式化輸出
    print(f"\n計算完成。")
    print(f"有效數字的總和為: {total_sum}")
    if invalid_entries:
        print(f"以下項目因格式無效而被忽略: {invalid_entries}")
    else:
        print("所有項目均為有效數字。")
                                

# 腳本層級的"全域"變數
LEGAL_AGE = 18

if __name__ == "__main__":
    name = input("你好，請問你叫什麼名字？ ")
    age_str = input(f"很高興認識你, {name}！請問你幾歲？ ")

    try:
        # 型別轉換
        age_int = int(age_str)
        
        # 在 try 區塊內定義的變數，其作用域仍屬於 if __name__ == "__main__"
        if age_int >= LEGAL_AGE:
            message = "你已經是成年人了！"
        else:
            message = "你還是個青少年！"
        
        # 使用 f-string
        print(f"{name}, {message}")

    except ValueError:
        # 異常捕捉
        print(f"錯誤：'{age_str}' 不是一個有效的年齡。請輸入數字。")
                                

if __name__ == "__main__":
    operation_count = 1 # 主程式區塊作用域

    print(f"--- 第 {operation_count} 次除法運算 ---")
    
    try:
        dividend_str = input("請輸入被除數: ")
        divisor_str = input("請輸入除數: ")

        # 型別轉換
        dividend = float(dividend_str)
        divisor = float(divisor_str)
        
        # 核心運算
        result = dividend / divisor

    except ValueError:
        # 捕捉型別錯誤
        print("錯誤：輸入無效，請確保輸入的是數字。")
    except ZeroDivisionError:
        # 捕捉除以零錯誤
        print("錯誤：除數不能為零。")
    else:
        # try 區塊無錯誤時執行
        print(f"計算成功！結果是： {dividend} / {divisor} = {result:.4f}")
    finally:
        # 無論如何都會執行
        print("計算結束。")
                                

import json
import csv

def process_student_data(json_file, csv_file):
    try:
        with open(json_file, 'r', encoding='utf-8') as f:
            students = json.load(f)
    except FileNotFoundError:
        print(f"錯誤: 找不到輸入檔案 {json_file}")
        return
    except json.JSONDecodeError:
        print(f"錯誤: {json_file} 格式不正確")
        return

    processed_data = []
    for student in students:
        name = student.get('name', 'N/A')
        student_id = student.get('student_id', 'N/A')
        scores = student.get('scores', [])
        
        if scores:
            average = sum(scores) / len(scores)
        else:
            average = 0.0
        
        processed_data.append([name, student_id, f"{average:.2f}"])

    try:
        with open(csv_file, 'w', newline='', encoding='utf-8') as f:
            writer = csv.writer(f)
            writer.writerow(['Name', 'Student ID', 'Average Score'])
            writer.writerows(processed_data)
        print(f"成功將結果寫入 {csv_file}")
    except IOError as e:
        print(f"寫入 CSV 檔案時發生錯誤: {e}")

if __name__ == "__main__":
    # 為了讓此範例可獨立執行，我們手動建立 JSON 檔案
    students_json_content = """
    [
        {"student_id": "S001", "name": "Alice", "scores": [85, 92, 78]},
        {"student_id": "S002", "name": "Bob", "scores": [90, 88, 94]},
        {"student_id": "S003", "name": "Charlie", "scores": [65, 75, 70]}
    ]
    """
    with open("students.json", "w") as f:
        f.write(students_json_content)

    process_student_data("students.json", "grades.csv")
                                

import json

class Contact:
    def __init__(self, name, phone):
        self.name = name
        self.phone = phone

    def to_dict(self):
        return {"name": self.name, "phone": self.phone}

    def __str__(self):
        return f"Name: {self.name}, Phone: {self.phone}"

class ContactBook:
    def __init__(self):
        self.contacts = []

    def add_contact(self, contact):
        self.contacts.append(contact)
        print(f"Added: {contact.name}")

    def display_all(self):
        if not self.contacts:
            print("Contact book is empty.")
            return
        print("\n--- All Contacts ---")
        for contact in self.contacts:
            print(contact)
        print("--------------------")

    def search_contact(self, name):
        for contact in self.contacts:
            if contact.name.lower() == name.lower():
                return contact
        return None

    def save_to_file(self, filename):
        with open(filename, 'w', encoding='utf-8') as f:
            json.dump([c.to_dict() for c in self.contacts], f, indent=4)
        print(f"Contacts saved to {filename}")

    def load_from_file(self, filename):
        try:
            with open(filename, 'r', encoding='utf-8') as f:
                data = json.load(f)
                self.contacts = [Contact(c['name'], c['phone']) for c in data]
            print(f"Contacts loaded from {filename}")
        except FileNotFoundError:
            print("No saved contacts found. Starting a new contact book.")
        except (json.JSONDecodeError, KeyError):
            print("Error reading file. File might be corrupt.")

if __name__ == '__main__':
    book = ContactBook()
    file = "my_contacts.json"
    book.load_from_file(file)

    c1 = Contact("Peter Parker", "123-456-7890")
    c2 = Contact("Tony Stark", "987-654-3210")
    book.add_contact(c1)
    book.add_contact(c2)
    
    book.display_all()

    found = book.search_contact("Peter Parker")
    if found:
        print(f"\nFound contact: {found}")

    book.save_to_file(file)
                                

import re
from collections import Counter

def analyze_log(log_file):
    # Regex to find lines containing ERROR or FATAL and capture the log level
    # The pattern looks for a line that contains the word ERROR or FATAL
    pattern = re.compile(r".* (ERROR|FATAL): .*")
    error_counts = Counter()

    try:
        with open(log_file, 'r', encoding='utf-8') as f:
            for line in f:
                match = pattern.match(line)
                if match:
                    log_level = match.group(1) # Group 1 is (ERROR|FATAL)
                    error_counts[log_level] += 1
                    print(f"Found match: {line.strip()}")
        
        print("\n--- Log Analysis Report ---")
        if error_counts:
            for level, count in error_counts.items():
                print(f"Total '{level}' messages: {count}")
        else:
            print("No ERROR or FATAL messages found.")
        print("-------------------------")

    except FileNotFoundError:
        print(f"Error: Log file '{log_file}' not found.")

if __name__ == "__main__":
    log_content = """
[2023-10-27 10:00:00] INFO: User 'admin' logged in.
[2023-10-27 10:01:15] WARNING: Disk space is running low.
[2023-10-27 10:02:30] ERROR: Database connection failed.
[2023-10-27 10:03:00] INFO: Request processed successfully.
[2023-10-27 10:05:00] FATAL: System shutting down due to critical failure.
[2023-10-27 10:06:45] ERROR: Payment gateway timeout.
"""
    with open("server.log", "w") as f:
        f.write(log_content.strip())
    
    analyze_log("server.log")
                                

# --- 檔案 1: converters.py ---
"""A module for various unit conversions."""

USD_TWD_RATE = 31.5

def usd_to_twd(usd_amount):
    """Converts US Dollars to New Taiwan Dollars."""
    if not isinstance(usd_amount, (int, float)):
        raise TypeError("Amount must be a number.")
    return usd_amount * USD_TWD_RATE

def celsius_to_fahrenheit(celsius):
    """Converts Celsius to Fahrenheit."""
    if not isinstance(celsius, (int, float)):
        raise TypeError("Temperature must be a number.")
    return (celsius * 9/5) + 32

# --- 檔案 2: main.py ---
# 假設 converters.py 和 main.py 在同一個資料夾

# 匯入自訂模組
import converters

if __name__ == "__main__":
    # 使用貨幣轉換函式
    dollars = 150
    taiwan_dollars = converters.usd_to_twd(dollars)
    print(f"${dollars} USD is approximately NT${taiwan_dollars:.2f}")

    # 使用溫度轉換函式
    temp_c = 25
    temp_f = converters.celsius_to_fahrenheit(temp_c)
    print(f"{temp_c}°C is equal to {temp_f}°F")

    # 測試錯誤處理
    try:
        converters.usd_to_twd("one hundred")
    except TypeError as e:
        print(f"\nCaught expected error: {e}")
                                

import json
import csv

class Product:
    def __init__(self, product_id, name, price):
        self.product_id = product_id
        self.name = name
        self.price = price

    def to_dict(self):
        return {'type': 'Product', 'product_id': self.product_id, 'name': self.name, 'price': self.price}

    def __str__(self):
        return f"ID: {self.product_id}, Name: {self.name}, Price: ${self.price}"

class Book(Product):
    def __init__(self, product_id, name, price, author):
        super().__init__(product_id, name, price)
        self.author = author

    def to_dict(self):
        data = super().to_dict()
        data['type'] = 'Book'
        data['author'] = self.author
        return data

    def __str__(self):
        return f"{super().__str__()}, Author: {self.author}"

class Electronics(Product):
    def __init__(self, product_id, name, price, warranty_months):
        super().__init__(product_id, name, price)
        self.warranty_months = warranty_months

    def to_dict(self):
        data = super().to_dict()
        data['type'] = 'Electronics'
        data['warranty_months'] = self.warranty_months
        return data

    def __str__(self):
        return f"{super().__str__()}, Warranty: {self.warranty_months} months"

class Inventory:
    def __init__(self):
        self.products = {} # {product_id: (product_object, quantity)}

    def add_product(self, product, quantity):
        if product.product_id in self.products:
            print(f"Error: Product ID {product.product_id} already exists.")
        else:
            self.products[product.product_id] = (product, quantity)
            print(f"Added {product.name} with quantity {quantity}.")

    def update_stock(self, product_id, quantity_change):
        if product_id in self.products:
            product, current_quantity = self.products[product_id]
            new_quantity = current_quantity + quantity_change
            if new_quantity < 0:
                print("Error: Stock cannot be negative.")
            else:
                self.products[product_id] = (product, new_quantity)
                print(f"Updated stock for {product.name}. New quantity: {new_quantity}")
        else:
            print(f"Error: Product ID {product_id} not found.")

    def generate_report(self, filename):
        with open(filename, 'w', newline='', encoding='utf-8') as f:
            writer = csv.writer(f)
            writer.writerow(['ID', 'Name', 'Type', 'Price', 'Quantity'])
            for pid, (product, quantity) in self.products.items():
                writer.writerow([pid, product.name, product.__class__.__name__, product.price, quantity])
        print(f"Inventory report saved to {filename}")

    def save_inventory(self, filename):
        data_to_save = {pid: (p.to_dict(), q) for pid, (p, q) in self.products.items()}
        with open(filename, 'w', encoding='utf-8') as f:
            json.dump(data_to_save, f, indent=4)
        print(f"Inventory saved to {filename}")

    def load_inventory(self, filename):
        try:
            with open(filename, 'r', encoding='utf-8') as f:
                loaded_data = json.load(f)
            
            self.products = {}
            for pid, (p_dict, q) in loaded_data.items():
                p_type = p_dict.pop('type')
                if p_type == 'Book':
                    product = Book(**p_dict)
                elif p_type == 'Electronics':
                    product = Electronics(**p_dict)
                else:
                    product = Product(**p_dict)
                self.products[pid] = (product, q)
            print(f"Inventory loaded from {filename}")
        except FileNotFoundError:
            print("No inventory file found. Starting fresh.")

if __name__ == '__main__':
    inventory = Inventory()
    inventory.load_inventory("inventory.json")
    
    if not inventory.products: # If file didn't exist
        b1 = Book("B001", "Python Crash Course", 29.99, "Eric Matthes")
        e1 = Electronics("E001", "Raspberry Pi 4", 55.00, 12)
        inventory.add_product(b1, 50)
        inventory.add_product(e1, 25)

    inventory.update_stock("B001", -5) # Sold 5 books
    inventory.generate_report("report.csv")
    inventory.save_inventory("inventory.json")
                                

import os
import re
import csv

def find_and_replace_in_files(root_dir, file_ext, pattern, replacement):
    log_data = []
    compiled_pattern = re.compile(pattern)

    if not os.path.isdir(root_dir):
        print(f"Error: Directory '{root_dir}' not found.")
        return

    for dirpath, _, filenames in os.walk(root_dir):
        for filename in filenames:
            if filename.endswith(file_ext):
                file_path = os.path.join(dirpath, filename)
                try:
                    with open(file_path, 'r', encoding='utf-8') as f:
                        content = f.read()
                    
                    new_content, num_subs = compiled_pattern.subn(replacement, content)

                    if num_subs > 0:
                        with open(file_path, 'w', encoding='utf-8') as f:
                            f.write(new_content)
                        log_data.append([file_path, num_subs])
                        print(f"Modified '{file_path}' ({num_subs} replacements).")

                except Exception as e:
                    print(f"Could not process file {file_path}: {e}")
    
    if log_data:
        with open('changelog.csv', 'w', newline='', encoding='utf-8') as f:
            writer = csv.writer(f)
            writer.writerow(['FilePath', 'ReplacementsCount'])
            writer.writerows(log_data)
        print("\nChangelog saved to changelog.csv")
    else:
        print("\nNo files were modified.")

if __name__ == '__main__':
    # --- Setup a test environment ---
    test_dir = "test_project"
    sub_dir = os.path.join(test_dir, "subdir")
    os.makedirs(sub_dir, exist_ok=True)
    with open(os.path.join(test_dir, "doc1.txt"), "w") as f:
        f.write("This is an old document with the old_keyword.")
    with open(os.path.join(sub_dir, "doc2.txt"), "w") as f:
        f.write("Another old_keyword here, and one more old_keyword.")
    with open(os.path.join(test_dir, "data.csv"), "w") as f:
        f.write("This file should be ignored.")
    # --- End of setup ---

    target_directory = test_dir
    extension = ".txt"
    # Replace all occurrences of 'old_keyword' with 'new_keyword'
    search_pattern = r"old_keyword"
    replace_with = "new_keyword"

    find_and_replace_in_files(target_directory, extension, search_pattern, replace_with)
                                

# 專案結構:
# /project
# |-- units/
# |   |-- __init__.py  (可以為空)
# |   |-- length.py
# |   `-- temperature.py
# |-- tests/
# |   |-- test_length.py
# |   `-- test_temperature.py
# `-- main.py

# --- units/length.py ---
def meters_to_feet(meters):
    return meters * 3.28084
def feet_to_meters(feet):
    return feet / 3.28084

# --- units/temperature.py ---
def celsius_to_fahrenheit(celsius):
    return (celsius * 9/5) + 32
def fahrenheit_to_celsius(fahrenheit):
    return (fahrenheit - 32) * 5/9

# --- tests/test_length.py ---
import unittest
# from units.length import meters_to_feet, feet_to_meters # 在實際執行時
# (為了展示，我們將函式定義在測試檔案中)
class TestLengthConversions(unittest.TestCase):
    def test_meters_to_feet(self):
        self.assertAlmostEqual(meters_to_feet(10), 32.8084)
    def test_feet_to_meters(self):
        self.assertAlmostEqual(feet_to_meters(32.8084), 10)

# --- tests/test_temperature.py ---
# import unittest
# from units.temperature import ... # 同上
class TestTemperatureConversions(unittest.TestCase):
    def test_celsius_to_fahrenheit(self):
        self.assertAlmostEqual(celsius_to_fahrenheit(0), 32)
        self.assertAlmostEqual(celsius_to_fahrenheit(100), 212)
    def test_fahrenheit_to_celsius(self):
        self.assertAlmostEqual(fahrenheit_to_celsius(32), 0)
        self.assertAlmostEqual(fahrenheit_to_celsius(212), 100)

# --- main.py ---
# from units import length, temperature # 在實際執行時
def main_menu():
    print("\nUnit Converter")
    print("1. Meters to Feet")
    print("2. Celsius to Fahrenheit")
    choice = input("Choose a conversion (or 'q' to quit): ")
    
    if choice == '1':
        value_str = input("Enter meters: ")
        try:
            meters = float(value_str)
            feet = length.meters_to_feet(meters)
            print(f"{meters}m is {feet:.2f}ft")
        except ValueError:
            print("Invalid input.")
    elif choice == '2':
        # ... 類似的邏輯 ...
        pass
    elif choice.lower() == 'q':
        return False
    return True

# if __name__ == '__main__':
#     while main_menu():
#         pass
#     print("Goodbye!")

# --- 為了讓此範例可獨立執行，將所有程式碼合併並執行測試 ---
if __name__ == "__main__":
    print("--- Running Unit Tests ---")
    # 為了展示，將函式定義在此
    def meters_to_feet(meters): return meters * 3.28084
    def feet_to_meters(feet): return feet / 3.28084
    def celsius_to_fahrenheit(celsius): return (celsius * 9/5) + 32
    def fahrenheit_to_celsius(fahrenheit): return (fahrenheit - 32) * 5/9
    
    suite = unittest.TestSuite()
    suite.addTest(unittest.makeSuite(TestLengthConversions))
    suite.addTest(unittest.makeSuite(TestTemperatureConversions))
    runner = unittest.TextTestRunner()
    runner.run(suite)
    print("\n--- Tests Completed ---")