我正在编写一个python脚本,启动几个进程和数据库连接。有时我想用Ctrl+C信号终止脚本,我想做一些清理工作。

在Perl中,我会这样做:

$SIG{'INT'} = 'exit_gracefully';

sub exit_gracefully {
    print "Caught ^C \n";
    exit (0);
}

如何在Python中进行类似操作?


用signal注册你的处理程序。信号是这样的:

#!/usr/bin/env python
import signal
import sys

def signal_handler(sig, frame):
    print('You pressed Ctrl+C!')
    sys.exit(0)

signal.signal(signal.SIGINT, signal_handler)
print('Press Ctrl+C')
signal.pause()

代码改编自这里。

更多关于信号的文档可以在这里找到。  

你可以通过捕获KeyboardInterrupt异常来处理CTRL+C。您可以在异常处理程序中实现任何清理代码。

你可以像对待其他异常一样对待它(KeyboardInterrupt)。创建一个新文件,并在shell中运行它,包含以下内容,看看我的意思:

import time, sys

x = 1
while True:
    try:
        print x
        time.sleep(.3)
        x += 1
    except KeyboardInterrupt:
        print "Bye"
        sys.exit()

您可以使用Python内置信号模块中的函数来设置Python中的信号处理程序。特别是信号。Signal (signalnum, handler)函数用于为信号signalnum注册处理函数。

来自Python的文档:

import signal
import time

def handler(signum, frame):
    print 'Here you go'

signal.signal(signal.SIGINT, handler)

time.sleep(10) # Press Ctrl+c here

作为一个上下文管理器:

import signal

class GracefulInterruptHandler(object):

    def __init__(self, sig=signal.SIGINT):
        self.sig = sig

    def __enter__(self):

        self.interrupted = False
        self.released = False

        self.original_handler = signal.getsignal(self.sig)

        def handler(signum, frame):
            self.release()
            self.interrupted = True

        signal.signal(self.sig, handler)

        return self

    def __exit__(self, type, value, tb):
        self.release()

    def release(self):

        if self.released:
            return False

        signal.signal(self.sig, self.original_handler)

        self.released = True

        return True

使用方法:

with GracefulInterruptHandler() as h:
    for i in xrange(1000):
        print "..."
        time.sleep(1)
        if h.interrupted:
            print "interrupted!"
            time.sleep(2)
            break

嵌套的处理程序:

with GracefulInterruptHandler() as h1:
    while True:
        print "(1)..."
        time.sleep(1)
        with GracefulInterruptHandler() as h2:
            while True:
                print "\t(2)..."
                time.sleep(1)
                if h2.interrupted:
                    print "\t(2) interrupted!"
                    time.sleep(2)
                    break
        if h1.interrupted:
            print "(1) interrupted!"
            time.sleep(2)
            break

网址:https://gist.github.com/2907502

另一个片段

将main作为main函数,将exit_elegant作为Ctrl+C处理程序

if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        pass
    finally:
        exit_gracefully()

我调整了@udi的代码来支持多个信号(没什么特别的):

class GracefulInterruptHandler(object):
    def __init__(self, signals=(signal.SIGINT, signal.SIGTERM)):
        self.signals = signals
        self.original_handlers = {}

    def __enter__(self):
        self.interrupted = False
        self.released = False

        for sig in self.signals:
            self.original_handlers[sig] = signal.getsignal(sig)
            signal.signal(sig, self.handler)

        return self

    def handler(self, signum, frame):
        self.release()
        self.interrupted = True

    def __exit__(self, type, value, tb):
        self.release()

    def release(self):
        if self.released:
            return False

        for sig in self.signals:
            signal.signal(sig, self.original_handlers[sig])

        self.released = True
        return True

这段代码支持键盘中断调用(SIGINT)和SIGTERM (kill <process>)

与Matt J的答案相反,我使用了一个简单的对象。这使我有可能将这个处理程序解析到需要安全停止的所有线程。

class SIGINT_handler():
    def __init__(self):
        self.SIGINT = False

    def signal_handler(self, signal, frame):
        print('You pressed Ctrl+C!')
        self.SIGINT = True


handler = SIGINT_handler()
signal.signal(signal.SIGINT, handler.signal_handler)

在其他地方

while True:
    # task
    if handler.SIGINT:
        break

就我个人而言,我不能使用try/,除非KeyboardInterrupt,因为我使用的是阻塞的标准套接字(IPC)模式。因此,SIGINT是被提示的,但只有在接收到套接字上的数据后才会出现。

设置信号处理程序的行为与此相同。

另一方面,这只适用于实际的终端。其他启动环境可能不接受Ctrl+C或预处理信号。

此外,在Python中有“异常”和“BaseException”,它们的区别在于解释器需要自己干净地退出,因此一些异常的优先级高于其他异常(异常派生自BaseException)

感谢已有的答案,但添加了signal.getsignal()

import signal

# store default handler of signal.SIGINT
default_handler = signal.getsignal(signal.SIGINT)
catch_count = 0

def handler(signum, frame):
    global default_handler, catch_count
    catch_count += 1
    print ('wait:', catch_count)
    if catch_count > 3:
        # recover handler for signal.SIGINT
        signal.signal(signal.SIGINT, default_handler)
        print('expecting KeyboardInterrupt')

signal.signal(signal.SIGINT, handler)
print('Press Ctrl+c here')

while True:
    pass

如果你想确保你的清理过程完成,我将通过使用SIG_IGN添加到Matt J的答案,这样进一步的SIGINT将被忽略,这将防止你的清理被打断。

import signal
import sys

def signal_handler(signum, frame):
    signal.signal(signum, signal.SIG_IGN) # ignore additional signals
    cleanup() # give your process a chance to clean up
    sys.exit(0)

signal.signal(signal.SIGINT, signal_handler) # register the signal with the signal handler first
do_stuff()