blocks|key|4621177|text|查看atexit模块：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4621178|http://docs.python.org/library/atexit.html|4621179|例如，如果我想在应用程序终止时打印一条消息：|4621180|import+atexit

def+exit_handler():
++++print+'My+application+is+ending!'

atexit.register(exit_handler)|code-block|syntax|javascript|4621181|请注意，这对于脚本的正常终止非常有效，但它不会在所有情况下都被调用(例如，致命的内部错误)。|4621182|entityMap|0|LINK|mutability|MUTABLE|url^0|2|6|0|0|16|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@$9|11|A|12|1|13]]|E|$]]|$1|H|3|I|5|6|7|14|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|15|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|16|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|G]]]]

Check out the <code>atexit</code> module:

<a href="http://docs.python.org/library/atexit.html" rel="noreferrer">http://docs.python.org/library/atexit.html</a>

For example, if I wanted to print a message when my application was terminating:

<pre><code>import atexit

def exit_handler():
 print 'My application is ending!'

atexit.register(exit_handler)
</code></pre>

Just be aware that this works great for normal termination of the script, but it won't get called in all cases (e.g. fatal internal errors).

blocks|key|1867763|text|如果您通过引发KeyboardInterrupt来停止脚本(例如，通过按Ctrl-C)，则可以将其捕获为标准异常。您也可以用同样的方式捕获SystemExit。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1867764|try:
++++...
except+KeyboardInterrupt:
++++#+clean+up
++++raise|code-block|syntax|javascript|1867765|我提到这一点只是为了让您了解它；这样做的“正确”方法是上面提到的atexit模块。|1867766|entityMap^0|7|H|1X|A|0|0|W|6|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

If you stop the script by raising a <code>KeyboardInterrupt</code> (e.g. by pressing Ctrl-C), you can catch that just as a standard exception. You can also catch <code>SystemExit</code> in the same way.

<pre><code>try:
 ...
except KeyboardInterrupt:
 # clean up
 raise
</code></pre>

I mention this just so that you know about it; the 'right' way to do this is the <code>atexit</code> module mentioned above.

blocks|key|1867772|text|如果你想让某个东西总是运行，即使是在出错的时候，可以像这样使用try:+finally:+-|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1867773|def+main():
++++try:
++++++++execute_app()
++++finally:
++++++++handle_cleanup()

if+__name__=='__main__':
++++main()|code-block|syntax|javascript|1867774|如果还想处理异常，可以在finally:之前插入except:|1867775|entityMap^0|V|D|0|0|C|8|O|7|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

If you want something to always run, even on errors, use <code>try: finally:</code> like this -

<pre><code>def main():
 try:
 execute_app()
 finally:
 handle_cleanup()

if __name__=='__main__':
 main()
</code></pre>

If you want to also handle exceptions you can insert an <code>except:</code> before the <code>finally:</code>

blocks|key|1871254|text|如果您拥有在整个程序生命周期中存在的类对象，则还可以使用__del__(self)方法从这些类中执行命令：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1871255|class+x:
def+__init__(self):
++++while+True:
++++++++print+("running")
++++++++sleep(1)

def+__del__(self):
++++print("destructuring")


a+=+x()|code-block|syntax|javascript|1871256|这也适用于正常的程序结束，如果执行被中止，肯定会有一些例外：|1871257|running
running
running
running
running
Traceback+(most+recent+call+last):
++File+"x.py",+line+14,+in+<module>
++++a+=+x()
++File+"x.py",+line+8,+in+__init__
++++sleep(1)
KeyboardInterrupt
destructuring|1871258|entityMap^0|S|D|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

If you have class objects, that exists during the whole lifetime of the program, you can also execute commands from the classes with the <code>__del__(self)</code> method:
<pre><code>class x:
def __init__(self):
 while True:
 print (&quot;running&quot;)
 sleep(1)

def __del__(self):
 print(&quot;destructuring&quot;)


a = x()
</code></pre>
this works on normal program end as well if the execution is aborted, for sure there will be some exceptions:
<pre><code>running
running
running
running
running
Traceback (most recent call last):
 File &quot;x.py&quot;, line 14, in &lt;module&gt;
 a = x()
 File &quot;x.py&quot;, line 8, in __init__
 sleep(1)
KeyboardInterrupt
destructuring
</code></pre>

How can you have a function or something that will be executed before your program quits? I have a script that will be constantly running in the background, and I need it to save some data to a file before it exits. Is there a standard way of doing this?

Doing something before program exit

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在你的程序退出之前，你怎么能有一个函数或者什么东西可以被执行呢？我有一个经常在后台运行的脚本，我需要它在文件退出之前将一些数据保存到文件中。有没有标准的方法来做这件事？

问在程序退出之前做一些事情
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