I would like to keep repeating/executing a script forever, until Ctrl+C is pressed. My code below doesn't work, it executes once and calls it finished. The .py file being executed is a unit test file.
import subprocess
import time
fileNames = [
'KeepRepeatingThisFile.py' ,
]
try:
while True:
for i in fileNames:
execfile(str(i))
time.sleep(20)
except KeyboardInterrupt:
pass
Last few lines of KeepRepeatingThisFile.py:
# Execute test
if __name__ == '__main__':
unittest.main()
Related
I posted a question about how to catch a "sudo shutdown -r 2" event in Python. I was sent to this thread: Run code in python script on shutdown signal .
I'm running a Raspberry Pi v2 with Jessy.
I have read about
signal
and have tried to follow the ideas in the above thread, but so far I have not been successful. Here is my code:
import time
import signal
import sys
def CloseAll(Code, Frame):
f = open('/mnt/usbdrive/output/TestSignal.txt','a')
f.write('Signal Code:' + Code)
f.write('Signal Frame:' + Frame)
f.write('\r\n')
f.close()
sys.exit(0)
signal.signal(signal.SIGTERM,CloseAll)
print('Program is running')
try:
while True:
#get readings from sensors every 15 seconds
time.sleep(15)
f = open('/mnt/usbdrive/output/TestSignal.txt','a')
f.write('Hello ')
f.write('\r\n')
f.close()
except KeyboardInterrupt:
f = open('/mnt/usbdrive/output/TestSignal.txt','a')
f.write('Done')
f.write('\r\n')
f.close()
The program runs in a "screen" session/window and reacts as expected to a CNTL-C. However, when I exit the screen session, leaving the program running, and enter "sudo shutdown -r 2", the Pi reboots as expected after 2 minutes, but the TestSignal.txt file does not show that the signal.SIGTERM event was processed.
What am I doing wrong? Or better yet, how can I trap the shutdown event, usually initiated by a cron job, and close my Python program running in a screen session gracefully?
When you do not try to await such an event, but in a parallel session send SIGTERMto that process (e.g. by calling kill -15 $PID on the process id $PID of the python script running) , you should see an instructive error message ;-)
Also the comment about the mount point should be of interest after you repaired the python errors (TypeError: cannot concatenate 'str' and 'int' objects).
Try something like:
import time
import signal
import sys
LOG_PATH = '/mnt/usbdrive/output/TestSignal.txt'
def CloseAll(Code, Frame):
f = open(LOG_PATH, 'a')
f.write('Signal Code:' + str(Code) + ' ')
f.write('Signal Frame:' + str(Frame))
f.write('\r\n')
f.close()
sys.exit(0)
signal.signal(signal.SIGTERM, CloseAll)
print('Program is running')
try:
while True:
# get readings from sensors every 15 seconds
time.sleep(15)
f = open(LOG_PATH, 'a')
f.write('Hello ')
f.write('\r\n')
f.close()
except KeyboardInterrupt:
f = open(LOG_PATH, 'a')
f.write('Done')
f.write('\r\n')
f.close()
as a starting point. If this works somehow on your system why not rewrite some portions like:
# ... 8< - - -
def close_all(signum, frame):
with open(LOG_PATH, 'a') as f:
f.write('Signal Code:%d Signal Frame:%s\r\n' % (signum, frame))
sys.exit(0)
signal.signal(signal.SIGTERM, close_all)
# 8< - - - ...
Edit: To further isolate the error and adapt more to production like mode, one might rewrite the code like this (given that syslog is running on the machine, which it should, but I never worked on devices of that kind):
#! /usr/bin/env python
import datetime as dt
import time
import signal
import sys
import syslog
LOG_PATH = 'foobarbaz.log' # '/mnt/usbdrive/output/TestSignal.txt'
def close_all(signum, frame):
"""Log to system log. Do not spend too much time after receipt of TERM."""
syslog.syslog(syslog.LOG_CRIT, 'Signal Number:%d {%s}' % (signum, frame))
sys.exit(0)
# register handler for SIGTERM(15) signal
signal.signal(signal.SIGTERM, close_all)
def get_sensor_readings_every(seconds):
"""Mock for sensor readings every seconds seconds."""
time.sleep(seconds)
return dt.datetime.now()
def main():
"""Main loop - maybe check usage patterns for file resources."""
syslog.syslog(syslog.LOG_USER, 'Program %s is running' % (__file__,))
try:
with open(LOG_PATH, 'a') as f:
while True:
f.write('Hello at %s\r\n' % (
get_sensor_readings_every(15),))
except KeyboardInterrupt:
with open(LOG_PATH, 'a') as f:
f.write('Done at %s\r\n' % (dt.datetime.now(),))
if __name__ == '__main__':
sys.exit(main())
Points to note:
the log file for the actual measurements is separate from the logging channel for operational alerts
the log file handle is safeguarded in context managing blocks and in usual operation is just kept open
for alerting the syslog channel is used.
as a sample for the message routing the syslog.LOG_USER on my system (OS X) gives me in all terminals a message, whilst the syslog.LOG_ERR priority message in signal handler only targets the system log.
should be more to the point during shutdown hassle (not opening a file, etc.)
The last point (5.) is important in case all processes receive a SIGTERM during shutdown, i.e. all want to do something (slowing things down), maybe screenalso does not accept any buffered input anymore (or does not flush), note stdout is block buffered not line buffered.
The decoupling of the output channels, should also ease the eventual disappearance of the mount point of the measurement log file.
I'm trying to run a pygame program using pythonw to avoid having the console window show up. This causes a weird issue related to print statements.
Basically, the program will just exit after a few seconds with no error message. The more printing I do, the faster it happens.
If I run it in idle or at the command prompt (or in linux) the program works fine. This problem only happens when launched with pythonw (right-click, Open With, pythonw).
I'm using python 2.7.11 on Windows XP 32-bit. pygame 1.9.1release.
Is there a workaround for this? Why does the program simply terminate with no error?
import pygame
from pygame.locals import *
succeeded, failed = pygame.init()
display_surface = pygame.display.set_mode((320, 240))
clock = pygame.time.Clock()
terminate = False
while terminate is False:
for event in pygame.event.get():
if event.type == QUIT:
terminate = True
area = display_surface.fill((0,100,0))
pygame.display.flip()
elapsed = clock.tick(20)
print str(elapsed)*20
pygame.quit()
You don't need to remove print statements. Save them for later debugging. ;-)
Two steps to solve this problem:
Firstly, keep all the code in py file - don't change it to pyw now; Say it is actualCode.py
Then, create a new file runAs.pyw with the following lines in it
# In runAs.pyw file, we will first send stdout to StringIO so that it is not printed
import sys # access to stdout
import StringIO # StringIO implements a file like class without the need of disc
sys.stdout = StringIO.StringIO() # sends stdout to StringIO (not printed anymore)
import actualCode # or whatever the name of your file is, see further details below
Note that, just importing actualCode runs the file, so, in actualCode.py you should not enclose the code which is executed, in what I call is it main running file condition. For example,
# In actualCode.py file
....
....
....
if __name__ == '__main__': # Don't use this condition; it evaluates to false when imported
... # These lines won't be executed when this file is imported,
... # So, keep these lines outside
# Note: The file in your question, as it is, is fine
I am writing some code that makes use of the multiprocessing module. However, since I am a newbie, what often happens is that some error pops up, putting a halt to the main application.
However, that applications' children still remain running, and I get a long, long list of running pythonw processes in my task manager list.
After an error occurs, what can I do to make sure all the child processes are killed as well?
There are two pieces to this puzzle.
How can I detect and kill all the child processes?
How can I make a best effort to ensure my code from part 1 is run whenever one process dies?
For part 1, you can use multiprocessing.active_children() to get a list of all the active children and kill them with Process.terminate(). Note the use of Process.terminate() comes with the usual warnings.
from multiprocessing import Process
import multiprocessing
def f(name):
print 'hello', name
while True: pass
if __name__ == '__main__':
for i in xrange(5):
p = Process(target=f, args=('bob',))
p.start()
# At user input, terminate all processes.
raw_input("Press Enter to terminate: ")
for p in multiprocessing.active_children():
p.terminate()
One solution to part 2 is to use sys.excepthook, as described in this answer. Here is a combined example.
from multiprocessing import Process
import multiprocessing
import sys
from time import sleep
def f(name):
print 'hello', name
while True: pass
def myexcepthook(exctype, value, traceback):
for p in multiprocessing.active_children():
p.terminate()
if __name__ == '__main__':
for i in xrange(5):
p = Process(target=f, args=('bob',))
p.start()
sys.excepthook = myexcepthook
# Sleep for a bit and then force an exception by doing something stupid.
sleep(1)
1 / 0
I am looking something like this.
If i have a method in a class, now that i accept 2 command line arguments (start, stop), so when i run python script.py start, it will start automatically, now after sometime if user enters script.py stop it should end gracefully, can it be done.
This is what i have tried to do
from multiprocessing import Process, Queue
from time import sleep
import sys
def start(name):
print('hello', name)
print "Sleeping for 60 sec"
# sleep (60)
if __name__ == '__main__':
p = Process(target=start, args=('bob',))
p.start()
Thanks
i want run two process child as
#!/usr/bin/env python
from multiprocessing import Process
import time
def method(namelog):
filelog = open(namelog,'w')
while True:
time.sleep(0.1)
filelog.write('test log anything \n')
if __name__ == '__main__':
p1 = Process(target=method, args=('log1.log',))
print "start process1"
p1.start()
p2 = Process(target=method, args=('log2.log',))
print "start process2"
p2.start()
result :
start process1
start process2
program create 2 file log1.log and log2.log
but not save data
i thing process created but it not work
help me !!!
You have to close your file for writing. Note that I changed the mode in open() from write to append.
Try this:
from multiprocessing import Process
import time
def method(namelog):
while True:
with open(namelog,'a') as filelog:
time.sleep(0.1)
filelog.write('test log anything \n')
if __name__ == '__main__':
p1 = Process(target=method, args=('log1.log',))
print "start process1"
p1.start()
p2 = Process(target=method, args=('log2.log',))
print "start process2"
p2.start()