Python进阶教程：文件操作与异常处理

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# 方式一：手动关闭
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f = open("data.txt", "r", encoding="utf-8")
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content = f.read()
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f.close()  # 一定要关闭文件
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# 方式二：with 语句（推荐，自动关闭）
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with open("data.txt", "r", encoding="utf-8") as f:
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    content = f.read()

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with open("data.txt", "r", encoding="utf-8") as f:
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    # 读取全部内容
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    content = f.read()
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    # 读取一行
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    # line = f.readline()
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    # 逐行读取（推荐大文件）
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    # for line in f:
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    #     print(line.strip())

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# 覆盖写入
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with open("output.txt", "w", encoding="utf-8") as f:
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    f.write("第一行
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")
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    f.write("第二行
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")
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# 追加写入
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with open("output.txt", "a", encoding="utf-8") as f:
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    f.write("追加的内容
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")

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try:
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    num = int(input("请输入数字："))
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    print(10 / num)
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except ValueError:
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    print("输入的不是数字！")
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except ZeroDivisionError:
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    print("不能除以零！")
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except Exception as e:
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    print(f"发生错误：{e}")

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try:
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    f = open("config.txt", "r", encoding="utf-8")
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    print(f.read())
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except FileNotFoundError:
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    print("文件不存在")
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else:
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    print("读取成功，没有异常")
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finally:
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    print("无论是否异常都会执行")
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    f.close()

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def check_age(age):
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    if age < 0:
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        raise ValueError("年龄不能为负数")
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    if age < 18:
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        raise Exception("未成年人禁止访问")
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    print("欢迎访问")
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try:
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    check_age(-5)
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except ValueError as e:
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    print(e)  # 年龄不能为负数

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import os
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# 判断文件是否存在
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print(os.path.exists("data.txt"))  # True / False
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# 重命名文件
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os.rename("old.txt", "new.txt")
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# 删除文件
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os.remove("temp.txt")
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# 创建目录
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os.makedirs("mydir", exist_ok=True)
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# 列出目录内容
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print(os.listdir("."))

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import os
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import time
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def log(message):
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    """将消息追加写入日志文件"""
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    with open("app.log", "a", encoding="utf-8") as f:
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        timestamp = time.strftime("%Y-%m-%d %H:%M:%S")
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        f.write(f"[{timestamp}] {message}
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")
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def divide(a, b):
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    try:
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        result = a / b
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        log(f"计算 {a}/{b} = {result}")
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        return result
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    except ZeroDivisionError:
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        log("错误：除数为零")
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        print("除数为零，记录到日志")
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# 测试
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divide(10, 2)   # 正常记录
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divide(10, 0)   # 记录错误
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print("查看 app.log 内容：")
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with open("app.log", "r", encoding="utf-8") as f:
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    print(f.read())