关于错误处理：在Python中捕获嵌套异常

Capture Nested Exceptions in Python

我有一组Python脚本，它们以嵌套的方式调用函数。对于这些函数中的每一个，我都有一个try，除了语句来捕获每个异常并打印它们。我想发送一封电子邮件警报，其中包含执行期间遇到的完整异常序列。例：

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import sys

def SendAlert(ErrorMessage):
try:
#send email alert with error message
#[...]
except:
print(str(sys.exc_info()))
return(sys.exc_info())

def ParentFunction():
try:
#call ChildFunction
ChildResult = ChildFunction()

#do stuff with ChildResult
#[...]
return ParentResult
except:
ErrorMessage = str(sys.exc_info())
print(ErrorMessage)
SendAlert(ErrorMessage)

def ChildFunction():
try:
#do stuff
#[...]
return ChildResult
except:
print(str(sys.exc_info()))
return(sys.exc_info())

#main
if __name__ == '__main__':
Result = ParentFunction()

如果ChildFunction中出现错误，上面的代码将表现如下，这是最嵌套的函数：

ChildFunction遇到异常，它将打印并返回
错误消息到ParentFunction
ParentFunction将失败，因为ChildResult包含错误消息而不是有效值
ParentFunction将触发和异常，并在电子邮件警报中发送自己的错误消息

除了来自ParentFunction的错误消息之外，我希望电子邮件警报包含来自ChildFunction的错误消息。请注意，我想避免在ParentFunction的except语句中将ChildResult变量传递给SendAlert函数，因为在现实生活中我的程序有很多嵌套函数，这意味着将每个函数的结果变量传递给除了声明。

你会如何实现这一目标？有没有办法访问整个程序触发的完整错误序列？

谢谢

相关讨论

你不需要返回用sys.exc_info获得的异常：我们可以重新提升它

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try:
# do stuff
# FIXME: we should avoid catching too broad exception
except Exception as err:
# do stuff with exception
raise err

所以你的例子看起来像

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def SendAlert(ErrorMessage):
try:
# send email alert with error message
# [...]
pass
# what kind of exceptions may occur while sending email?
except Exception as err:
print(err)
raise err

def ParentFunction():
try:
# call ChildFunction
ChildResult = ChildFunction()

ParentResult = ChildResult
# do stuff with ChildResult
# [...]
return ParentResult
# FIXME: we should avoid catching too broad exception
except Exception as err:
ErrorMessage = str(err)
# why do we need to print again?
print(ErrorMessage)
SendAlert(ErrorMessage)

def ChildFunction():
try:
ChildResult = 0
# do stuff
# [...]

# let's raise `ZeroDivisionError`

ChildResult /= 0

return ChildResult
# FIXME: we should avoid catching too broad exception
except Exception as err:
print(err)
raise err

# main
if __name__ == '__main__':
Result = ParentFunction()

进一步改进

对于打印完整错误回溯，我们可以使用logging模块

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import logging

logging.basicConfig(level=logging.DEBUG)

logger = logging.getLogger(__name__)

def SendAlert(ErrorMessage):
try:
# send email alert with error message
# [...]
pass
# what kind of exceptions may occur while sending email?
except Exception as err:
logger.exception('Error while sending email')
# we're not receiving values from this function
raise err

def ParentFunction():
try:
# call ChildFunction
ChildResult = ChildFunction()

ParentResult = ChildResult
# do stuff with ChildResult
# [...]
return ParentResult
# FIXME: we should avoid catching too broad exception
except Exception as err:
# this will log full error traceback
# including `ChildFunction`
logger.exception('Error in ParentFunction')
ErrorMessage = str(err)
SendAlert(ErrorMessage)

def ChildFunction():
ChildResult = 0
# do stuff
# [...]

# e. g. let's raise `ZeroDivisionError`
ChildResult /= 0

return ChildResult

# main
if __name__ == '__main__':
Result = ParentFunction()

它只是冰山一角，logging很棒，你绝对应该使用它。

进一步阅读

记录HOWTO，
SMTPHandler，用于通过SMTP发送电子邮件错误