python的單例模式

1.這裡介紹的python的單例模式有兩種方式，一種方式是win32event的CreateMutex來實現，另外就是定義一個全域變數

第一種實現方式可以參考這裡http://code.activestate.com/recipes/474070-creating-a-single-instance-application/

from win32event import CreateMutexfrom win32api import CloseHandle, GetLastErrorfrom winerror import ERROR_ALREADY_EXISTSclass 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 singleinstancefrom sys import exit# do this at beginnig of your applicationmyapp = singleinstance()# check is another instance of same program runningif 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"## end of http://code.activestate.com/recipes/474070/ }}}

2.對於方法2，網上的方法很多，這裡就簡單的摘抄一個，http://dev.firnow.com/course/1_web/webjs/200855/114357.html

 

代碼

class Logger(object):
    log = None
    @staticmethod
def new():
if not Logger.log:
            Logger.log = Logger()
return Logger.log
def write(self, v):
print str(self), v

log1 = Logger.new()
log1.write("log1")

log2 = Logger.new()
log2.write("log2") 

“”“
分析：很簡單的實現方法，把當前執行個體儲存起來，下次執行個體化時再返回以前的執行個體。但是在判斷的時候保證不了是安全執行緒的。放在這裡，先有個思路。
"""