decorator and signal handler

[stalex]

Hi all,

I wrote the following code since I want to try using a decorator to
install signal handler:

## The test.py script
#################
import os
import time
import signal

def sigHandler(sid):
def handler(f):
signal.signal(sid, f)
return f
return handler

class Test(object):
@sigHandler(signal.SIGTERM)
def _sigHandler(self, signalId, currentFrame):
print "Received:", signalId

if __name__ == "__main__":
print "pid:", os.getpid()

t = Test()
time.sleep(300)

# From terminal, say A
####################
$ python test.py
pid: 1234

# From terminal, say B
###################
$ kill -TERM 1234

After issuing the kill command from terminal B, the process of test.py
from terminal A is terminated.
Python print out some exception message as following:
Traceback (most recent call last):
File "a.py", line 22, in <module>
time.sleep(300)
TypeError: _sigHandler() takes exactly 3 arguments (2 given)

At a guess, I think the decorator I defined did not pass the 'self' as
the first argument to _sigHandler() method, did it? And I have no idea
of how to write a correct one. Any suggestion?

 

[Michele Simionato]

Hi all,

I wrote the following code since I want to try using a decorator to
install signal handler:

I do have a decorator for exactly that purpose in my code. Here it is:

def on(sig):
'''
A factory of decorators for signal handlers. An example of usage
is

@on(signal.SIGTERM)
def termination(frame):
print 'sent SIGTERM'
raise SystemExit

Code calling termination.signal() will send a SIGTERM signal to
the
main thread, which in turns will call the termination handler,
which
will print a message and raise SystemExit.
'''
def handler_decorator(handler):
'Install the handler and add a .signal function attribute to
it'
signal.signal(sig, lambda signum, frame : handler(frame))
handler.signal = lambda : os.kill(os.getpid(), sig)
return handler
return handler_decorator

Michele Simionato