python的单例模式

1.这里介绍的python的单例模式有两种方式，一种方式是win32event的CreateMutex来实现，另外就是定义一个全局变量

第一种实现方式可以参考这里http://code.activestate.com/recipes/474070-creating-a-single-instance-application/

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"
## end of http://code.activestate.com/recipes/474070/ }}}

2.对于方法2，网上的方法很多，这里就简单的摘抄一个，http://dev.firnow.com/course/1_web/webjs/200855/114357.html

 

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：很简单的实现方法，把当前实例保存起来，下次实例化时再返回以前的实例。但是在判断的时候保证不了是线程安全的。放在这里，先有个思路。
"""