Python 异常处理中的九个常见错误及其解决办法

def print_hello()
    print("Hello, world!")
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 File "<stdin>", line 1
    def print_hello()
                     ^
SyntaxError: invalid syntax
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def print_hello():
    print("Hello, world!")  # 添加了冒号
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def say_hello(name):
print(f"Hello, {name}!")
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 File "<stdin>", line 2
print(f"Hello, {name}!")
     ^
IndentationError: expected an indented block
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def say_hello(name):
    print(f"Hello, {name}!")  # 正确的缩进
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num = 5
text = "hello"
result = num + text
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Traceback (most recent call last):
  File "<stdin>", line 3, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'
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num = 5
text = "hello"
# 将数字转换为字符串
result = str(num) + text
print(result)  # 输出: 5hello
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print(age)
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NameError: name 'age' is not defined
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age = 25
print(age)  # 正确
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num = 5
print(num.length)
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AttributeError: 'int' object has no attribute 'length'
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text = "hello"
print(len(text))  # 使用内置函数 len() 而不是 .length
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person = {"name": "Alice", "age": 25}
print(person["gender"])
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KeyError: 'gender'
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person = {"name": "Alice", "age": 25}
# 使用 get() 方法
print(person.get("gender", "Unknown"))  # 输出: Unknown
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numbers = [1, 2, 3]
print(numbers[3])
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IndexError: list index out of range
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numbers = [1, 2, 3]
try:
    print(numbers[3])  # 索引超出范围
except IndexError:
    print("索引超出范围")
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result = 10 / 0
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ZeroDivisionError: division by zero
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numerator = 10
denominator = 0

try:
    result = numerator / denominator
except ZeroDivisionError:
    print("除数不能为零")
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with open("nonexistent.txt", "r") as file:
    content = file.read()
    print(content)
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FileNotFoundError: [Errno 2] No such file or directory: 'nonexistent.txt'
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filename = "nonexistent.txt"

try:
    with open(filename, "r") as file:
        content = file.read()
        print(content)
except FileNotFoundError:
    print(f"文件 '{filename}' 不存在")
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import logging

# 配置日志记录器
logging.basicConfig(filename="app.log", level=logging.ERROR)

def log_action(action, user_id):
    try:
        with open("users.txt", "r") as file:
            users = file.readlines()
            if any(user.strip() == user_id for user in users):
                logging.info(f"{action} - User ID: {user_id}")
                return True
            else:
                raise ValueError("无效的用户ID")
    except FileNotFoundError:
        logging.error("找不到用户文件")
    except IOError:
        logging.error("无法读取用户文件")
    except Exception as e:
        logging.error(f"未知错误: {e}")
    return False

# 测试用例
if __name__ == "__main__":
    # 创建测试文件
    with open("users.txt", "w") as file:
        file.write("alice\n")
        file.write("bob\n")

    # 正常情况
    if log_action("登录成功", "alice"):
        print("登录成功")
    
    # 无效用户ID
    if not log_action("登录失败", "invalid_user"):
        print("登录失败")

    # 文件不存在
    if not log_action("登录失败", "alice"):
        print("登录失败")

    # 删除测试文件
    import os
    os.remove("users.txt")
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登录成功
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登录失败
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登录失败
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ERROR:root:无效的用户ID
ERROR:root:找不到用户文件
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