Python __exit__ 方法中异常信息的有效日志记录与处理

class MyContextManager:
    def __init__(self, log_file_path):
        self.log_file = open(log_file_path, 'a')

    def __enter__(self):
        self.log_file.write('Entering context...\n')
        return self

    def __exit__(self, exception_type, exception_value, traceback_obj):
        log_message = "Exiting context."
        if exception_type is not None:
            # 当有异常发生时，构建简洁的异常信息
            error_details = f"{exception_type.__name__}: {exception_value}"
            log_message += f" due to {error_details}"
        else:
            log_message += " normally."

        self.log_file.write(f'{log_message}\n')
        self.log_file.close()
        # 返回 False（或不返回任何东西）表示异常将被重新抛出
        # 返回 True 表示异常已被处理，不应重新抛出
        return False

# 示例使用
with MyContextManager("app.log") as manager:
    print("Inside context...")
    result = 10 / 0 # 这将引发 ZeroDivisionError

# 查看 app.log 文件内容，将包含类似 "Exiting context due to ZeroDivisionError: division by zero" 的信息

import traceback
import os

class MyDetailedContextManager:
    def __init__(self, log_file_path):
        self.log_file_path = log_file_path
        self.log_file = None

    def __enter__(self):
        self.log_file = open(self.log_file_path, 'a')
        self.log_file.write('Entering detailed context...\n')
        return self

    def __exit__(self, exception_type, exception_value, traceback_obj):
        if exception_type is not None:
            # 格式化完整的堆栈跟踪
            full_trace = "".join(traceback.format_exception(exception_type, exception_value, traceback_obj))
            self.log_file.write(f'Exiting due to exception:\n{full_trace}\n')
        else:
            self.log_file.write('Exiting normally.\n')

        if self.log_file:
            self.log_file.close()
        return False # 重新抛出异常

# 清理旧日志文件以便观察新输出
if os.path.exists("detailed_app.log"):
    os.remove("detailed_app.log")

# 示例使用
with MyDetailedContextManager("detailed_app.log") as manager:
    print("Inside detailed context...")
    def inner_function():
        raise ValueError("Something went wrong in inner function")
    inner_function()

# 查看 detailed_app.log 文件，将包含完整的堆栈跟踪信息

import traceback

class MyFormatExcContextManager:
    def __init__(self, log_file_path):
        self.log_file = open(log_file_path, 'a')

    def __enter__(self):
        self.log_file.write('Entering format_exc context...\n')
        return self

    def __exit__(self, exception_type, exception_value, traceback_obj):
        if exception_type is not None:
            # 注意：这里调用 format_exc() 会获取当前活动异常，
            # 在 __exit__ 中通常就是由 with 块抛出的异常
            full_trace = traceback.format_exc()
            self.log_file.write(f'Exiting due to exception (using format_exc):\n{full_trace}\n')
        else:
            self.log_file.write('Exiting normally.\n')
        self.log_file.close()
        return False

# 示例使用
# with MyFormatExcContextManager("format_exc_app.log") as manager:
#     print("Inside format_exc context...")
#     1 / 0 # 同样会记录完整的堆栈跟踪

import traceback
import sys
import os

class MyPrintTbContextManager:
    def __init__(self, log_file_path):
        self.log_file_path = log_file_path
        self.log_file = None

    def __enter__(self):
        self.log_file = open(self.log_file_path, 'a')
        self.log_file.write('Entering print_tb context...\n')
        return self

    def __exit__(self, exception_type, exception_value, traceback_obj):
        if exception_type is not None:
            self.log_file.write(f'Exiting due to {exception_type.__name__}: {exception_value}\n')
            self.log_file.write('Full traceback (using print_tb):\n')
            # 直接将追溯信息打印到日志文件
            traceback.print_tb(traceback_obj, file=self.log_file)
            self.log_file.write('\n') # 添加一个空行以分隔
        else:
            self.log_file.write('Exiting normally.\n')

        if self.log_file:
            self.log_file.close()
        return False

# 清理旧日志文件以便观察新输出
if os.path.exists("print_tb_app.log"):
    os.remove("print_tb_app.log")

# 示例使用
with MyPrintTbContextManager("print_tb_app.log") as manager:
    print("Inside print_tb context...")
    # 模拟一个嵌套调用来生成更长的追溯
    def another_func():
        raise IndexError("Index out of bounds")
    another_func()

# 查看 print_tb_app.log 文件，将看到直接打印的追溯信息

import traceback

class MyTracebackExceptionContextManager:
    def __init__(self, log_file_path):
        self.log_file = open(log_file_path, 'a')

    def __enter__(self):
        self.log_file.write('Entering TracebackException context...\n')
        return self

    def __exit__(self, exception_type, exception_value, traceback_obj):
        if exception_type is not None:
            # 正确地使用 TracebackException
            te = traceback.TracebackException(exception_type, exception_value, traceback_obj)
            # format_exception_only 返回一个字符串列表，通常只有一个元素
            exception_summary = "".join(te.format_exception_only()).strip()
            self.log_file.write(f'Exiting due to (using TracebackException): {exception_summary}\n')
        else:
            self.log_file.write('Exiting normally.\n')
        self.log_file.close()
        return False

# 示例使用
# with MyTracebackExceptionContextManager("traceback_exception_app.log") as manager:
#     print("Inside TracebackException context...")
#     list_data = [1, 2]
#     print(list_data[5]) # IndexError