How to store a variable when a script is executing for next time execution?

[Avnesh Shakya]

hi,
   I am running a python script and it will create a file name like filename0.0.0 and If I run it again then new file will create one more like filename0.0.1...... my code is-

i = 0
for i in range(1000):
    try:
        with open('filename%d.%d.%d.json'%(0,0,i,)): pass
        continue
    except IOError:
        dataFile = file('filename%d.%d.%d.json'%(0,0,i,), 'a+')
        break
But It will take more time after creating many files, So i want to store value of last var "i" in a variable so that when i run my script again then I can use it. for example-
                 my last created file is filename0.0.27 then it should store 27 in a variable and when i run again then new file should be created 0.0.28 according to last value "27", so that i could save time and it can create file fast..

Please give me suggestion for it.. How is it possible?
Thanks