python的pageobject设计模式的前提需要了解什么是类：

#encoding:utf-8
class Light:
    _SN=""
    @property
    def SN(self):
        return self._SN
    @SN.setter
    def SN(self,SN):
        if SN(self.SN):
            if self._SN=="":
                self._SN=SN
            else:
                print("已有值，不可修改")
li=Light
print("SN=%s"%li.SN)

class Logger():
    def __init__(self,filename):
        self.filename=filename

    def write(self,msg):
        print("想某个文件中写入数据:%s"%msg)


#encoding:utf-8
from pageobject.demo01 import Logger

log=Logger("test_log.log")
log.write("tt")
log.write("yy")
log.write("uu")

log=Logger("test_log1.log")
log.write("tt1")
log.write("yy1")
log.write("uu1")