Python异常处理try-except用法：怎么捕获错误并记录日志

# 错误写法：裸 except 会捕获系统中断信号，导致终端无法正常终止程序
try:
    process_critical_data()
except:
    pass  # 吞没所有错误与中断信号，造成僵尸进程与数据黑洞

import logging
from logging.handlers import RotatingFileHandler

# 1. 获取以当前模块名为标识的 logger 实例
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)  # 允许捕获的最低日志级别

# 2. 定义统一的日志格式（时间、级别、模块名、所在行号、消息）
log_formatter = logging.Formatter(
    fmt="%(asctime)s [%(levelname)s] [%(name)s:%(lineno)d] - %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S"
)

# 3. 创建输出到控制台的 Handler
console_handler = logging.StreamHandler()
console_handler.setLevel(logging.INFO)
console_handler.setFormatter(log_formatter)

# 4. 创建自动滚动的文件 Handler（单文件最大 5MB，保留 3 个备份）
file_handler = RotatingFileHandler(
    filename="app_error.log",
    maxBytes=5 * 1024 * 1024,
    backupCount=3,
    encoding="utf-8"
)
file_handler.setLevel(logging.ERROR)
file_handler.setFormatter(log_formatter)

# 5. 绑定到 logger
if not logger.handlers:
    logger.addHandler(console_handler)
    logger.addHandler(file_handler)

import json
import logging
import os
import sys

# -------------------------------------------------------------
# 1. 初始化标准日志配置
# -------------------------------------------------------------
logger = logging.getLogger("BatchProcessor")
logger.setLevel(logging.DEBUG)

formatter = logging.Formatter(
    fmt="%(asctime)s [%(levelname)s] [%(name)s] - %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S"
)

console_handler = logging.StreamHandler(sys.stdout)
console_handler.setFormatter(formatter)
if not logger.handlers:
    logger.addHandler(console_handler)

# -------------------------------------------------------------
# 2. 核心业务处理函数（带完整异常拦截与日志）
# -------------------------------------------------------------
def process_user_record(file_path: str, record_id: int) -> dict:
    """
    读取并解析指定用户的记录文件。
    演示精准捕获、业务参数注入、日志记录与资源释放。
    """
    file_obj = None
    logger.info("开始处理用户记录任务: RecordID=%d, FilePath=%s", record_id, file_path)

    try:
        # 仅将易发生 I/O 与解析错误的代码放入 try 块
        file_obj = open(file_path, "r", encoding="utf-8")
        data = json.load(file_obj)

        # 模拟可能出现的数据格式校验
        if "score" not in data:
            raise KeyError("数据包缺失必要字段: 'score'")

        score_value = float(data["score"])
        normalized_ratio = 100.0 / score_value  # 若 score_value 为 0 将引发 ZeroDivisionError

    except FileNotFoundError:
        # 精确捕获特定已知异常：记录 WARNING 级日志并返回默认占位数据
        logger.warning("目标记录文件不存在，跳过本次解析: RecordID=%d, Path=%s", record_id, file_path)
        return {"record_id": record_id, "status": "skipped", "reason": "file_not_found"}

    except (json.JSONDecodeError, KeyError) as e:
        # 数据格式畸变：记录 ERROR 级日志并附带完整堆栈
        logger.exception("数据格式畸变导致解析失败: RecordID=%d, ErrorType=%s", record_id, type(e).__name__)
        return {"record_id": record_id, "status": "failed", "reason": str(e)}

    except Exception as e:
        # 未预期的严重运行时异常：完整记录堆栈并重新抛出，防止脏数据入库
        logger.exception("处理记录时遭遇未知致命异常: RecordID=%d", record_id)
        raise

    else:
        # 当且仅当 try 内无任何异常时执行的逻辑
        logger.info("用户记录解析成功: RecordID=%d, NormalizedRatio=%.2f", record_id, normalized_ratio)
        return {"record_id": record_id, "status": "success", "ratio": normalized_ratio}

    finally:
        # 确保打开的文件句柄一定得到关闭释放
        if file_obj and not file_obj.closed:
            file_obj.close()
            logger.debug("已安全关闭文件资源: Path=%s", file_path)

2026-10-30 10:06:12 [INFO] [BatchProcessor] - 开始处理用户记录任务: RecordID=8041, FilePath=test_bad.json
2026-10-30 10:06:12 [ERROR] [BatchProcessor] - 数据格式畸变导致解析失败: RecordID=8041, ErrorType=JSONDecodeError
Traceback (most recent call last):
  File "batch_data_loader.py", line 33, in process_user_record
    data = json.load(file_obj)
  File "/usr/lib/python3.9/json/__init__.py", line 293, in load
    return loads(fp.read(),
  File "/usr/lib/python3.9/json/__init__.py", line 346, in loads
    return _default_decoder.decode(s)
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
2026-10-30 10:06:12 [DEBUG] [BatchProcessor] - 已安全关闭文件资源: Path=test_bad.json