A fast but simple implement of no database storage

LocalStorage.py

import marshal,json,os
import threading

class LocalStorage(object):
    def __init__(self,filename="datafile.dat"):
        self.filename = filename

    def init(self):
        if os.path.exists(self.filename):
            inf = open(self.filename,"rb")
            self.data = marshal.load(inf)
            inf.close()
        else:
            self.data = {}
        self.save()

    def default_callback(string):
        return json.loads(string)

    def store(self,string,callback = default_callback):
        dic = callback(string)
        # for domin in dic:
        #     self.data.setdefault(domin,[]).append(dic[domin])
        self.data.setdefault(dic["domin"],[]).append(dic["path"])
    
    def query(self,domin):
        return json.dumps(self.data.get(domin,""))

    def save(self):
        threading.Timer(300,self.save).start()
        print "I saved"
        self._dumps(self.data,self.filename)

    def _dumps(self,data,filename):
        ouf = open(filename,'wb')
        marshal.dump(data,ouf)
        ouf.close()