Singleton using python under ms-windows

From ASPN python cookbook
Submitter: Dragan Jovelic

URL:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/474070
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from win32event import CreateMutex
from win32api import CloseHandle, GetLastError
from winerror import ERROR_ALREADY_EXISTS

class singleinstance:
""" Limits application to single instance """

def __init__(self):
    self.mutexname = "testmutex_{D0E858DF-985E-4907-B7FB-8D732C3FC3B9}"
    self.mutex = CreateMutex(None, False, self.mutexname)
    self.lasterror = GetLastError()

def aleradyrunning(self):
    return (self.lasterror == ERROR_ALREADY_EXISTS)

def __del__(self):
    if self.mutex:
        CloseHandle(self.mutex)


#---------------------------------------------#
# sample usage:
#

from singleinstance import singleinstance
from sys import exit

# do this at beginnig of your application
myapp = singleinstance()

# check is another instance of same program running
if myapp.aleradyrunning():
print "Another instance of this program is already running"
exit(0)

# not running, safe to continue...
print "No another instance is running, can continue here"