I would like to know how to I exit from Python without having an traceback dump on the output.
I still want want to be able to return an error code but I do not want to display the traceback log.
I want to be able to exit using exit(number) without trace but in case of an Exception (not an exit) I want the trace.
You are presumably encountering an exception and the program is exiting because of this (with a traceback). The first thing to do therefore is to catch that exception, before exiting cleanly (maybe with a message, example given).
Try something like this in your main routine:
import sys, traceback
def main():
try:
do main program stuff here
....
except KeyboardInterrupt:
print "Shutdown requested...exiting"
except Exception:
traceback.print_exc(file=sys.stdout)
sys.exit(0)
if __name__ == "__main__":
main()
Perhaps you're trying to catch all exceptions and this is catching the SystemExit exception raised by sys.exit()?
import sys
try:
sys.exit(1) # Or something that calls sys.exit()
except SystemExit as e:
sys.exit(e)
except:
# Cleanup and reraise. This will print a backtrace.
# (Insert your cleanup code here.)
raise
In general, using except: without naming an exception is a bad idea. You'll catch all kinds of stuff you don't want to catch -- like SystemExit -- and it can also mask your own programming errors. My example above is silly, unless you're doing something in terms of cleanup. You could replace it with:
import sys
sys.exit(1) # Or something that calls sys.exit().
If you need to exit without raising SystemExit:
import os
os._exit(1)
I do this, in code that runs under unittest and calls fork(). Unittest gets when the forked process raises SystemExit. This is definitely a corner case!
import sys
sys.exit(1)
The following code will not raise an exception and will exit without a traceback:
import os
os._exit(1)
See this question and related answers for more details. Surprised why all other answers are so overcomplicated.
This also will not do proper cleanup, like calling cleanup handlers, flushing stdio buffers, etc. (thanks to pabouk for pointing this out)
something like import sys; sys.exit(0) ?
It's much better practise to avoid using sys.exit() and instead raise/handle exceptions to allow the program to finish cleanly. If you want to turn off traceback, simply use:
sys.trackbacklimit=0
You can set this at the top of your script to squash all traceback output, but I prefer to use it more sparingly, for example "known errors" where I want the output to be clean, e.g. in the file foo.py:
import sys
from subprocess import *
try:
check_call([ 'uptime', '--help' ])
except CalledProcessError:
sys.tracebacklimit=0
print "Process failed"
raise
print "This message should never follow an error."
If CalledProcessError is caught, the output will look like this:
[me#test01 dev]$ ./foo.py
usage: uptime [-V]
-V display version
Process failed
subprocess.CalledProcessError: Command '['uptime', '--help']' returned non-zero exit status 1
If any other error occurs, we still get the full traceback output.
I would do it this way:
import sys
def do_my_stuff():
pass
if __name__ == "__main__":
try:
do_my_stuff()
except SystemExit, e:
print(e)
Use the built-in python function quit() and that's it.
No need to import any library.
I'm using python 3.4
What about
import sys
....
....
....
sys.exit("I am getting the heck out of here!")
No traceback and somehow more explicit.
# Pygame Example
import pygame, sys
from pygame.locals import *
pygame.init()
DISPLAYSURF = pygame.display.set_mode((400, 300))
pygame.display.set_caption('IBM Emulator')
BLACK = (0, 0, 0)
GREEN = (0, 255, 0)
fontObj = pygame.font.Font('freesansbold.ttf', 32)
textSurfaceObj = fontObj.render('IBM PC Emulator', True, GREEN,BLACK)
textRectObj = textSurfaceObj.get_rect()
textRectObj = (10, 10)
try:
while True: # main loop
DISPLAYSURF.fill(BLACK)
DISPLAYSURF.blit(textSurfaceObj, textRectObj)
for event in pygame.event.get():
if event.type == QUIT:
pygame.quit()
sys.exit()
pygame.display.update()
except SystemExit:
pass
Related
None of these are kill -9 or anything close. What's the answer?
import sys
import os
try:
exit()
sys.exit()
os._exit()
quit()
except:
print("THIS SHOULD NOT RUN")
It's ridiculous of the Python language if any try-catch wrapping of an abort() or anything like it prevent's it from being able to die.
That's not something that exists in any other language that I know. abort() is an emergency safety measure.
Continuing from what already has been explained by #Mike Scotty:
Picking one: (sys.exit())
sys.exit() raises an exception, namely SystemExit. That's why you land in the except-block.
Example:
import sys
try:
sys.exit()
except:
print(sys.exc_info()[0])
OUTPUT:
<class 'SystemExit'>
In depth:
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
OUTPUT:
sys.exit() worked as expected
Source
Try CTRL+C while in the script, should do the trick
Well, I don't like the way Python handles this but I've found a solution and it's actually kill -9:
Disclaimer: Unfortunately, you have to start and run the process as root.
os.system("sudo kill -9 " + str(os.getpid()))
Thank you guys for seeing my post.
First, the following is my code:
import os
print("You can create your own message for alarm.")
user_message = input(">> ")
print("\n<< Sample alarm sound >>")
for time in range(0, 3):
os.system('say ' + user_message) # this code makes sound.
print("\nOkay, The alarm has been set.")
"""
##### My problem is here #####
##### THIS IS NOT STOPPED #####
while True:
try:
os.system('say ' + user_message)
except KeyboardInterrupt:
print("Alarm stopped")
exit(0)
"""
My problem is that Ctrl + C does not work!
I tried changing position of try block, and making signal(SIGINT) catching function.
But those also does not work.
I have seen https://stackoverflow.com/a/8335212/5247212, https://stackoverflow.com/a/32923070/5247212, and other several answers about this problem.
I am using MAC OS(10.12.3) and python 3.5.2.
This is expected behaviour, as os.system() is a thin wrapper around the C function system(). As noted in the man page, the parent process ignores SIGINT during the execution of the command. In order to exit the loop, you have to manually check the exit code of the child process (this is also mentioned in the man page):
import os
import signal
while True:
code = os.system('sleep 1000')
if code == signal.SIGINT:
print('Awakened')
break
However, the preferred (and more pythonic) way to achieve the same result is to use the subprocess module:
import subprocess
while True:
try:
subprocess.run(('sleep', '1000'))
except KeyboardInterrupt:
print('Awakened')
break
Your code would then look like something like this:
import subprocess
print("You can create your own message for alarm.")
user_message = input(">> ")
print("\n<< Sample alarm sound >>")
for time in range(0, 3):
subprocess.run(['say', user_message]) # this code makes sound.
print("\nOkay, The alarm has been set.")
while True:
try:
subprocess.run(['say', user_message])
except KeyBoardInterrupt:
print("Alarm terminated")
exit(0)
As an added note, subprocess.run() is only available in Python 3.5+. You can use subprocess.call() to achieve the same effect in older versions of Python.
Also catch "SystemExit"
except (KeyboardInterrupt, SystemExit):
print("Alarm stopped")
The problem seems to be that Ctrl+C is captured by the subprocess you call via os.system. This subprocess reacts correspondingly, probably by terminating whatever it is doing. If so, the return value of os.system() will be not zero. You can use that to break the while loop.
Here's an example that works with me (substituting say by sleep):
import os
import sys
while True:
try:
if os.system('sleep 1 '):
raise KeyboardInterrupt
except KeyboardInterrupt:
print("Alarm stopped")
sys.exit(0)
If Ctrl-C is captured by the subprocess, which is the case here, the simplest solution is to check the return value of os.system(). For example in my case it returns value of 2 if Ctrl-C stops it, which is a SIGINT code.
import os
while True:
r = os.system(my_job)
if r == 2:
print('Stopped')
break
elif r != 0:
print('Some other error', r)
I would like the user to use control-c to close a script, but when control-c is pressed it shows the error and reason for close (which make sense). Is there a way to have my own custom output to the screen rather than what is shown? Not sure how to handle that specific error.
You could use try..except to catch KeyboardInterrupt:
import time
def main():
time.sleep(10)
if __name__ == '__main__':
try:
main()
except KeyboardInterrupt:
print('bye')
use the signal module to define a handler for the SIGINT signal:
import signal
import sys
def sigint_handler(signal_number, stack_frame):
print('caught SIGINT, exiting')
sys.exit(-1)
signal.signal(signal.SIGINT, sigint_handler)
raw_input('waiting...')
For general purpose code, handling the KeyboardInterrupt should suffice. For advanced code, such as threading, it is a whole different story. Here's a simple example.
http://docs.python.org/2/library/exceptions.html#exceptions.KeyboardInterrupt
try:
while 1:
x = raw_input("Type something or press CTRL+C to end: ")
print repr(x)
except KeyboardInterrupt:
print "\nWe're done here."
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?
Check out the atexit module:
http://docs.python.org/library/atexit.html
For example, if I wanted to print a message when my application was terminating:
import atexit
def exit_handler():
print 'My application is ending!'
atexit.register(exit_handler)
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).
If you want something to always run, even on errors, use try: finally: like this -
def main():
try:
execute_app()
finally:
handle_cleanup()
if __name__=='__main__':
main()
If you want to also handle exceptions you can insert an except: before the finally:
If you stop the script by raising a KeyboardInterrupt (e.g. by pressing Ctrl-C), you can catch that just as a standard exception. You can also catch SystemExit in the same way.
try:
...
except KeyboardInterrupt:
# clean up
raise
I mention this just so that you know about it; the 'right' way to do this is the atexit module mentioned above.
If you have class objects, that exists during the whole lifetime of the program, you can also execute commands from the classes with the __del__(self) method:
class x:
def __init__(self):
while True:
print ("running")
sleep(1)
def __del__(self):
print("destructuring")
a = x()
this works on normal program end as well if the execution is aborted, for sure there will be some exceptions:
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
This is a version adapted from other answers.
It should work (not fully tested) with graceful exits, kills, and PyCharm stop button (the last one I can confirm).
import signal
import atexit
def handle_exit(*args):
try:
... do computation ...
except BaseException as exception:
... handle the exception ...
atexit.register(handle_exit)
signal.signal(signal.SIGTERM, handle_exit)
signal.signal(signal.SIGINT, handle_exit)
I was hoping that putting 'sys.exit(1)' and catching it later like this will work.
xml_open()
try:
run(reloader=True, host='localhost', port=8080)
except SystemExit:
xml_save()
print "Exited ..."
Is there any other solution to exit these python micro-frameworks to exit from inside
the handlers ?
If its not being handled then check whether Its really executes sys.exist(1) statement,
because It may happen some other exception raised which is not being handled try this....
xml_open()
try:
run(reloader=True, host='localhost', port=8080)
except SystemExit:
xml_save()
print "Exited ..."
except Exception, e:
print "ohhh no.......",str(e)
import pdb
pdb.post_mortem()
sys.exit(-1)
In case this is still an issue for you, check my answer here for a clean solution of stopping the bottle framework.
From my limited experience, sys.exit() should work when reloader is turned off. Otherwise, reloader will reload the code on sys.exit() and your application will be resumed. Of course, I might be wrong about why sys.exit() doesn't work, but for me it worked when I turned off the reloader.