我对python还比较陌生,我一直在处理以下问题。
我有一个脚本,它逐个处理文件,并根据输入文件名将输出写入单独的文件。有时我需要破坏脚本,但我想让它完成当前文件的处理,然后终止(以避免结果文件的信息不完整)。如何在python中编码这种行为?
这是我试过的。
a)试除块
x = 1
print "Script started."
while True:
try:
print "Processing file #",x,"started...",
# do something time-cosnuming
time.sleep(1)
x += 1
print " finished."
except KeyboardInterrupt:
print "Bye"
print "x=",x
sys.exit()
sys.exit()
输出:
Script started.
Processing file # 1 started... finished.
Processing file # 2 started... finished.
Processing file # 3 started... Bye
x= 3
迭代3没有优雅地完成。
b)系统例外挂钩
OriginalExceptHook = sys.excepthook
def NewExceptHook(type, value, traceback):
global Terminator
Terminator = True
if type == KeyboardInterrupt:
#exit("\nExiting by CTRL+C.") # this line was here originally
print("\n\nExiting by CTRL+C.\n\n")
else:
OriginalExceptHook(type, value, traceback)
sys.excepthook = NewExceptHook
global Terminator
Terminator = False
x = 1
while True:
print "Processing file #",x,"started...",
# do something time-cosnuming
time.sleep(1)
x += 1
print " finished."
if Terminator:
print "I'll be back!"
break
print "Bye"
print "x=",x
sys.exit()
输出:
Script started.
Processing file # 1 started... finished.
Processing file # 2 started... finished.
Processing file # 3 started...
Exiting by CTRL+C.
迭代3没有优雅地完成。
UPD 1
@mguijar,我稍微修改了一下代码,如下所示:
import time, sys
x = 1
print "Script started."
stored_exception=None
while True:
try:
print "Processing file #",x,"started...",
# do something time-cosnuming
time.sleep(1)
print "Processing file #",x,"part two...",
time.sleep(1)
print " finished."
if stored_exception:
break
x += 1
except KeyboardInterrupt:
print "[CTRL+C detected]",
stored_exception=sys.exc_info()
print "Bye"
print "x=",x
if stored_exception:
raise stored_exception[0], stored_exception[1], stored_exception[2]
sys.exit()
输出(在win7-64位上使用“python 2.7.6::anaconda 2.0.0(64位)”进行测试):
Script started.
Processing file # 1 started... Processing file # 1 part two... finished.
Processing file # 2 started... Processing file # 2 part two... finished.
Processing file # 3 started... [CTRL+C detected] Processing file # 3 started... Processing file # 3 part two... finished.
Bye
x= 3
Traceback (most recent call last):
File "test2.py", line 12, in <module>
time.sleep(1)
KeyboardInterrupt
在这种情况下,有效地重新启动了迭代3,这看起来很奇怪,并且不是所需的行为。有没有可能避免这种情况?
我删除了“print”语句中的逗号,并添加了更多内容,以查看迭代是否真正重新启动:
import time, sys
x = 1
y = 0
print "Script started."
stored_exception=None
while True:
try:
y=x*1000
y+=1
print "Processing file #",x,y,"started..."
y+=1
# do something time-cosnuming
y+=1
time.sleep(1)
y+=1
print "Processing file #",x,y,"part two..."
y+=1
time.sleep(1)
y+=1
print " finished.",x,y
y+=1
if stored_exception:
break
y+=1
x += 1
y+=1
except KeyboardInterrupt:
print "[CTRL+C detected]",
stored_exception=sys.exc_info()
print "Bye"
print "x=",x
print "y=",y
if stored_exception:
raise stored_exception[0], stored_exception[1], stored_exception[2]
sys.exit()
输出为:
Script started.
Processing file # 1 1001 started...
Processing file # 1 1004 part two...
finished. 1 1006
Processing file # 2 2001 started...
Processing file # 2 2004 part two...
[CTRL+C detected] Processing file # 2 2001 started...
Processing file # 2 2004 part two...
finished. 2 2006
Bye
x= 2
y= 2007
Traceback (most recent call last):
File "test2.py", line 20, in <module>
time.sleep(1)
KeyboardInterrupt
最佳答案
我只需要使用一个异常处理程序,它将捕获
存储异常。然后,在迭代完成时,如果出现异常
挂起时,我将中断循环并重新引发异常(以允许正常异常
把握机会)。
这项工作(用python 2.7测试):
x = 1
print "Script started."
stored_exception=None
while True:
try:
print "Processing file #",x,"started...",
# do something time-cosnuming
time.sleep(1)
print " finished."
if stored_exception:
break
x += 1
except KeyboardInterrupt:
stored_exception=sys.exc_info()
print "Bye"
print "x=",x
if stored_exception:
raise stored_exception[0], stored_exception[1], stored_exception[2]
sys.exit()
编辑:正如在评论中所看到的,这个答案对于最初的海报是不满意的,这里有一个基于线程的解决方案:
import time
import sys
import threading
print "Script started."
class MyProcessingThread(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
def run(self):
print "Processing file #",x,"started...",
# do something time-cosnuming
time.sleep(1)
print " finished."
for x in range(1,4):
task = MyProcessingThread()
task.start()
try:
task.join()
except KeyboardInterrupt:
break
print "Bye"
print "x=",x
sys.exit()