python sys.exit 在尝试中不起作用
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python sys.exit not working in try
提问by onlyvinish
Python 2.7.5 (default, Feb 26 2014, 13:43:17)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> try:
... sys.exit()
... except:
... print "in except"
...
in except
>>> try:
... sys.exit(0)
... except:
... print "in except"
...
in except
>>> try:
... sys.exit(1)
... except:
... print "in except"
...
in except
Why am not able to trigger sys.exit() in try, any suggestions...!!!
为什么我不能在尝试中触发 sys.exit()，任何建议......！！！
The code posted here has all the version details.
此处发布的代码包含所有版本详细信息。
I have tried all possible ways i know to trigger it, but i failed. It gets to 'except' block.
我已经尝试了我知道的所有可能的方法来触发它，但我失败了。它进入“除外”块。
Thanks in advance..
提前致谢..
采纳答案by tamasgal
sys.exit()raises an exception, namely SystemExit. That's why you land in the except-block.
sys.exit()引发异常，即SystemExit. 这就是你降落在except-block的原因。
See this example:
看这个例子：
import sys
try:
sys.exit()
except:
print(sys.exc_info()[0])
This gives you:
这给你：
<type 'exceptions.SystemExit'>
Although I can't imagine that one has any practical reason to do so, you can use this construct:
尽管我无法想象有任何实际理由这样做，但您可以使用以下结构：
import sys
try:
sys.exit() # this always raises SystemExit
except SystemExit:
print("sys.exit() worked as expected")
except:
print("Something went horribly wrong") # some other exception got raised
回答by Kasramvd
based on python wiki :
基于python wiki：
Since exit()ultimately “only” raises an exception, it will only exit the process when called from the main thread, and the exception is not intercepted.
由于exit()最终“只”抛出异常，所以只有从主线程调用时才会退出进程，不会拦截异常。
And:
和：
The
exitfunction is not called when the program is killed by a signal, when a Python fatal internal error is detected, or whenos._exit()is called.
exit当程序被信号杀死、检测到 Python 致命内部错误或被调用时，不会调用该函数os._exit()。
Therefore, If you use sys.exit()within a tryblock python after raising the SystemExitexception python refuses of completing the exits's functionality and executes the exceptionblock.
因此，如果在引发异常后sys.exit()在try块中使用SystemExitpython 将拒绝完成exits的功能并执行exception块。
Now, from a programming perspective you basically don't need to put something that you know definitely raises an exception in a tryblock. Instead you can either raise a SystemExitexception manually or as a more Pythonic approach if you don't want to loose the respective functionalities of sys.exit()like passing optional argument to its constructor you can call sys.exit()in a finally, elseor even exceptblock.
现在，从编程的角度来看，您基本上不需要将您知道肯定会引发异常的内容放入try块中。相反，SystemExit如果您不想失去sys.exit()将可选参数传递给其构造函数的相应功能，您可以手动引发异常或作为更 Pythonic 的方法，您可以sys.exit()在 a finally，else甚至except块中调用。
Method 1 (not recommended)
方法一（不推荐）
try:
# do stuff
except some_particular_exception:
# handle this exception and then if you want
# do raise SystemExit
else:
# do stuff and/or do raise SystemExit
finally:
# do stuff and/or do raise SystemExit
Method 2 (Recommended):
方法二（推荐）：
try:
# do stuff
except some_particular_exception:
# handle this exception and then if you want
# do sys.exit(stat_code)
else:
# do stuff and/or do sys.exit(stat_code)
finally:
# do stuff and/or do sys.exit(stat_code)
