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

[Jussi Piitulainen]

Avnesh Shakya writes:

> 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..

You could get a list of all filenames that match the pattern. Extract
the last components as numbers, and add 1 to the maximum.

  i = 1 + max(int(name.split('.')[-1])
              for name in glob.glob('filename.0.0.*))

That assumes that there already is at least one such file and all such
files have a last component that can be parsed as an int. Take an
appropriate amount of care.

Or you could also create a file, say lastname.0.0.31, to track the
name, and when you find it there, create filename.0.0.32 and replace
lastname.0.0.32; panic if there is more than one lastname.0.0.*, or
fewer than one.

Or as above but track with nextname.0.0.31 to create filename.0.0.31
and replace the tracking name with nextname.0.0.32 for the next file.

Or save the number somewhere else.